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gtexan02
02-05-2009, 01:46 PM
My main wish for the offseason is a ball-hawking safety. Frequently my posts are countered with the argument that average safeties can be made to look great with an a good pass rush.

So to find out if interceptions really are the result of a good pash rush, I looked at the stats from last year:

The top 5 teams last year for intereceptions were:
1. Baltimore (11th in sacks)
2. Cleveland (30th in sacks)
3. Chicago (22nd in sacks)
4. Greenbay (25th in sacks)
5. Tampa Bay (20th in sacks)


The bottom 5 teams last year were:
28. Buffalo (28th in sacks)
29. Seattle (10th in sacks)
30. Dallas (1st in sacks)
31. Denver (26th in sacks)
32. Detroit (16th in sacks)

The average sack ranking for a top 5 INT team was 21.6
The average sack ranking for a bottom 5 INT team was 16.2



Surprised? It makes logical sense that a team with a good pass rush would force a QB to make more poor decisions. But teams often plan accordingly, and as it turns out, teams with good pass rush actually get fewer interceptions. This is probably because teams playing against a team with a good pass rush use short drop backs, quick outs, and more runs to counteract the good pass rush.

A lot of interception takeaways is more the result of a good secondary. It does not depend entirely on the pass rush, as people seem to believe.

Wolf
02-05-2009, 01:53 PM
to add to your list(nice job by the way) .. I wonder what those teams did in the form of knockdowns and hurries?

I know sacks are nice and a good measuring stick,but sometimes it is more about disruption


Mario would be a good example on our team, he might not have as many sacks as the year before (not much but 2), but if I recall he created a lot of havok

gtexan02
02-05-2009, 01:54 PM
to add to your list(nice job by the way) .. I wonder what those teams did in the form of knockdowns and hurries?

Yeah, I really wish those stats were easier to find. All I have is NFL.com and ESPN. Anyone have a better stat site?

I think Dallas is the most interesting example. They have an incredible pass rush, but last season had a horrible secondary. And the result is that even a 60 sack season cannot move them past third from last.

Baltimore, on the other hand, has a ball-hawking secondary. They did not have to get many sacks to get their INTs

dalemurphy
02-05-2009, 02:00 PM
My main wish for the offseason is a ball-hawking safety. Frequently my posts are countered with the argument that average safeties can be made to look great with an a good pass rush.

So to find out if interceptions really are the result of a good pash rush, I looked at the stats from last year:

The top 5 teams last year for intereceptions were:
1. Baltimore (11th in sacks)
2. Cleveland (30th in sacks)
3. Chicago (22nd in sacks)
4. Greenbay (25th in sacks)
5. Tampa Bay (20th in sacks)


The bottom 5 teams last year were:
28. Buffalo (28th in sacks)
29. Seattle (10th in sacks)
30. Dallas (1st in sacks)
31. Denver (26th in sacks)
32. Detroit (16th in sacks)

The average sack ranking for a top 5 INT team was 21.6
The average sack ranking for a bottom 5 INT team was 16.2



Surprised? It makes logical sense that a team with a good pass rush would force a QB to make more poor decisions. But teams often plan accordingly, and as it turns out, teams with good pass rush actually get fewer interceptions. This is probably because teams playing against a team with a good pass rush use short drop backs, quick outs, and more runs to counteract the good pass rush.

A lot of interception takeaways is more the result of a good secondary. It does not depend entirely on the pass rush, as people seem to believe.


THe first thing I noticed is that all top 5 teams run fairly unique defenses that put players in position for INTS:

Baltimore and Cleveland[B]- both run a 3-4.. So, though Cleveland had a poor pass rush, I'd guess a number of INTs happened as a direct result of the zone blitzing they do.

[B]Chicago and Tampa Bay- both run the Cover 2... So, that system allows a lot of gambling by the CBs. Also, both teams were good against the run which probably means they got thrown on a lot.

Green Bay- they have special talent at CB and also play a more agressive Man coverage defense than anyone in the NFL.


Also, I don't think sack totals are the best indicator of a good pass rush. Clearly, though, scheme adoes have a significant impact on how many INTs a team comes away with. As a Texan fan, that's what is so exciting! Our scheme on defense has been SH*T!! It, the talent, and the aggressiveness will all be better next year. Yeah!

Interesting that Dallas was so bad with the scheme and pass rush they have. First, that does indicate their horrific play at safety. Also, perhaps they shouldn't have been so anxious to let JReeves go. They certainly could have used him last year. When Newman missed time, he would have been the best CB on their team.

TexansSeminole
02-05-2009, 02:23 PM
It may be more complete to incorporate the QBs quarterback rating and completion percentage against those defenses. Sometimes QBs don't throw INTs in the face of pressure but throw the ball away.

gtexan02
02-05-2009, 02:26 PM
It may be more complete to incorporate the QBs quarterback rating and completion percentage against those defenses. Sometimes QBs don't throw INTs in the face of pressure but throw the ball away.

That would give you a better idea of how much a good pass rush hurts a passing offense, but I was specifically interested in finding out if Interceptions were the result of a pass rush.

In addition to having very low sack totals every year, the Texans never seem to get many takeaways through the air. I always wondered if the two were related, but it seems like even the #1 pass rush doesn't guarantee you a lot of INTs. It takes a ballhawk in the secondary to pull those down

But just for fun:

Top 5 Teams in QB rating allowed (low number)
1. Baltimore (11th in sacks)
2. Pittsburgh (2nd in sacks)
3. Tennessee (5th in sacks)
4. Green Bay (25th in sacks)
5. Philadelphia (3rd in sacks)

Worst 5 Teams in QB rating allowed (high number)
28. Jacksonville (20th in sacks)
29. Seattle (10th in sacks)
30. Arizona (14th in sacks)
31. Denver (26th in sacks)
32. Detroit (16th in sacks)

The average sack ranking for a top QB rating team was 9.2
The average sack ranking for a bottom 5 QB rating team was 17.2

So in this, have a good pass rush certainly helps your pass defense. But it does not result in more turnovers. This makes sense, too, I think

One other interesting thing to note is that getting a lot of INTs does not necessarily equate to being a good pass defense team

TexansSeminole
02-05-2009, 02:30 PM
That would give you a better idea of how much a good pass rush hurts a passing offense, but I was specifically interested in finding out if Interceptions were the result of a pass rush.

In addition to having very low sack totals every year, the Texans never seem to get many takeaways through the air. I always wondered if the two were related, but it seems like even the #1 pass rush doesn't guarantee you a lot of INTs. It takes a ballhawk in the secondary to pull those down

Yea, I was just getting ahead of myself I guess, haha.

I think your right. A pass rush may give those guys more opportunities but you still need a ballhawk to actually make the interception.

IlliniJen
02-05-2009, 03:16 PM
Do you think that analyzing one season worth of stats will give you enough information to make a reliable assumption off of?

I would say you'd need at least 5 years of data to look at, in case this year was an anomoly in any way. It was indeed a strange year.

gtexan02
02-05-2009, 03:23 PM
Do you think that analyzing one season worth of stats will give you enough information to make a reliable assumption off of?

I would say you'd need at least 5 years of data to look at, in case this year was an anomoly in any way. It was indeed a strange year.

lol, are you trying to get me fired! :) 5 years :pirate:

I don't have time to do the full on stats, but I will say that looking back just by glancing at the stats seems to indicate that you may be right.

There are always a couple of odd balls (a team with a ton of sacks that didn't snag many INTs, or a team with tons of INTs that generated a weak pass rush), but the trend doesn't seem to support last years numbers if you glance back at the last few years.

That being said, its hard to account for teams like Cincinnatti(2007) who was 6th in INTs, 32nd in sacks or Miami (2006) who was 3rd in sacks, 31st in INTs.

To do a real analysis, we'd need to graph number of sacks by number of INTs over the last 5 years for every NFL team and see if there any sort of trend. Maybe I'll do that tonight

Bulluck53
02-05-2009, 03:32 PM
We can have fun with this.

Looking at Net Yards per Passing Attempt Allowed [(Passing Yards-Sack Yards)/(Passing Attempts-Times Sacked)] compared to league leaders in sacks, the top five went like this...

NY/A
Steelers.....Ravens
Eagles.....Titans
Cowboys

Sacks
Cowboys.....Steelers
Eagles.....Vikings
Titans

and then Interceptions

Ravens.....Browns
Packers.....Bears
Bucs

Bulluck53
02-05-2009, 03:43 PM
And after looking at those statistics as far back as '04 there is no consistent correlation between the three. We need to find QB pressures in order to get the result we're looking for.

gg no re
02-05-2009, 03:55 PM
Has the off-season gotten this boring already?

Bulluck53
02-05-2009, 03:57 PM
Haha so true, but I'm still getting rid of the bad taste form last year (its in the past now)

And besides, what better way to pass the time than talking in-depth statistics from years passed?

b0ng
02-05-2009, 03:57 PM
And after looking at those statistics as far back as '04 there is no consistent correlation between the three. We need to find QB pressures in order to get the result we're looking for.

That's a hard stat to find since I don't think that the NFL keeps track of hurries, knockdowns, etc. I think Football Outsiders is the place that might have that.

gtexan02
02-05-2009, 04:26 PM
Do you think that analyzing one season worth of stats will give you enough information to make a reliable assumption off of?

I would say you'd need at least 5 years of data to look at, in case this year was an anomoly in any way. It was indeed a strange year.

Alright Jen! Ask and ye shall receive :)

So I tabulated all the results for every team between 2004 and 2008 (5 years)
I plotted number of sacks vs. number of interceptions, and then looked for a correlation. Here is the resulting data plot:

http://img11.imageshack.us/img11/6826/statscl6.jpg

Sacks are plotted on the x-axis, INTs on the y
As you can probably tell from the graph, there is a slight positive trend, implying that more sacks = more interceptions.

However, this trend was not statistically significant.
(R = 0.14, N = 160, P > 0.05)

What this means is that we cannot conclude that more sacks results in more interceptions. And as we go further back into the data, we would expect to corroborate this result.

If you asked me what I believe, I personally think this says that more sacks does slightly increase your odds for more turnovers through the air. Our p value is pretty close to the significance level cut off, so with more numbers we may actually result in a real trend.

The important piece of information is that there is not a clear, steep trend between the two. There are way too many points on the far left (low sack numbers) with huge INTs and vice versa for me to believe the two are strongly linked.

While a good pass rush probably helps INTs, this says to me that a good secondary makes its opportunities regardless of who the front four (or three) are.

This is surprising, because I think a lot of people just sort of assume that a strong pass rush results in tons of INT opportunities.... and this just isn't the case

TimeKiller
02-05-2009, 06:10 PM
If hurries and D-line deflections were available I'd much like to see a graph (;)) correlating hurries to sacks or deflections to ints.

Logic would say a Dline with it's hands up causes tip drills and more ints. Certainly it counts as an INT, but it's not exactly like a corner jumping a route and may be inflating a normal secondary into a good one.

I think a large portion of hurries to go with a large portion of sacks is the true measure of a pass rush instead of sacks alone. Lots of hurries means the Dline was getting after folks, not just "Well, we had to get back there eventually" type of sacks.

I nominate this the most interesting thread of the offseason. I know it's early but this is just interesting. Good job gtex, gotta spread the rep though...

infantrycak
02-05-2009, 06:59 PM
That's a hard stat to find since I don't think that the NFL keeps track of hurries, knockdowns, etc. I think Football Outsiders is the place that might have that.

Stats, Inc. keeps them but only I believe for their reporter and team clientele. Gotta give the media something to be "special" with.

brakos82
02-05-2009, 07:09 PM
Alright Jen! Ask and ye shall receive :)

So I tabulated all the results for every team between 2004 and 2008 (5 years)
I plotted number of sacks vs. number of interceptions, and then looked for a correlation. Here is the resulting data plot:

http://img11.imageshack.us/img11/6826/statscl6.jpg

Sacks are plotted on the x-axis, INTs on the y
As you can probably tell from the graph, there is a slight positive trend, implying that more sacks = more interceptions.

However, this trend was not statistically significant.
(R = 0.14, N = 160, P > 0.05)

What this means is that we cannot conclude that more sacks results in more interceptions. And as we go further back into the data, we would expect to corroborate this result.

If you asked me what I believe, I personally think this says that more sacks does slightly increase your odds for more turnovers through the air. Our p value is pretty close to the significance level cut off, so with more numbers we may actually result in a real trend.

The important piece of information is that there is not a clear, steep trend between the two. There are way too many points on the far left (low sack numbers) with huge INTs and vice versa for me to believe the two are strongly linked.

While a good pass rush probably helps INTs, this says to me that a good secondary makes its opportunities regardless of who the front four (or three) are.

This is surprising, because I think a lot of people just sort of assume that a strong pass rush results in tons of INT opportunities.... and this just isn't the case

The scary thing is... I know what all of that means... :hide:

Thorn
02-05-2009, 08:03 PM
gtexan02 if I could give you rep for the work you did on that post, I would. :texflag:

Ole Miss Texan
02-05-2009, 08:36 PM
Dude... that is awesome. You should totally go get a Phd or something. ;)
Someone give the man some Rep cuz I can't!

That's really interesting stuff. And I can now see why/how that's the case.

However, think about this! If a team has a lot of sacks, that means they tackle the QB in the backfield while he has the ball, thus giving his team a 0% chance of making an interception. The more sacks you get, that's the less throws a QB is making and less chance for a Defense to actually make an interception.

Har har!!:pirate:

That's gotta be why the Texans told Mario to go get some sacks. I think Richard Smith was saying to Weaver "Don't sack him, let him get rid of the ball, that way we MIGHT get an interception... better yet Anthony... drop into coverage."

Ole Miss Texan
02-05-2009, 08:40 PM
The scary thing is... I know what all of that means... :hide:

Not me, I had statistics from 6-8:30 every Tue/Thur night. All I was thinking about was food and how much my Prof looked like Rick Moranis from Honey, I Shrunk the Kids.
http://videodetective.com/photos/150/00632702_.jpg

76Texan
02-05-2009, 09:39 PM
Good work gtexan02, and a nice thread! :cool:

Wolf
02-05-2009, 09:47 PM
i'd rep if i could (must spread it first)

Texanmike02
02-05-2009, 11:28 PM
How did I miss a statistical discussion? Wow, I'm a little late in the game. Oh yeah 12 hours shifts for 9 days in a row.

If you want my take, here it goes.

Interceptions are a rare occurrence. They are dependent on several things. First the QB has to make a mistake. We're going to assume that often times this is a mistake due to either disruption by the DL or a blitzing DB/LB or having a route disrupted. Second you need a DB (usually) to make a catch. Often the reason they are DB's and not receivers is that they don't have the hands to make the catches (among other reasons).

The idea of comparing it to QB rating is exceptional in this situation if you ask me. But rather than comparing teams/season you might try (sacks+hurries+knockdowns) to QB ratings in individual games. if someone can get me the number (damn 12 hour shifts) I'll make sense of them. The problem with using just sacks in this equation, is that I don't think its pressure from the side that makes the difference. Often the QB can step up into the pocket. Sacks are great don't get me wrong, but the QB just goes down. If you're looking to affect him, get pressure in his face.

I did a writeup a while back and went and looked it up. It doesn't really answer the question so much as highlight how difficult what you're trying to assess on defense. There are too many factors. Its kind of like the old "bikini wear among women and short wear among men are both directly coorelated to ice cream sales in Miami." Obviously men and women get hungry for ice cream when they see the opposite sex dressed in a piece of floss... (the obvious factor left out is the fact that when its hot you wear shirts/bathing suits AND eat ice cream.

Here's something to chew on though: This was born in another thread when Relianttexan asked me "If your going to judge the colts run defense on how they played in the playoffs then why not judge our defense in yds allowed the last 13 games of the season in which they were ranked 12th not 23rd.Or how bout we judge them the last 10 games of the season in which they were a top 10 D." I had pretty much ignored that "fact" because I didn't think it was possible that it was true. So this whole post is basically an answer to that question, but because of the scope it entails, I felt it was worthy of its own thread. This post will probably come in several parts because I see it being a lengthy but worthy read.

There is no standard for comparing defenses. You can rank them a number of ways. Ranking them by points allowed doesn't always work because its possible that the team's offense puts them in a bad position. So then you turn to yards. But then you have those bend but don't break situations.

My first inclination, when I read this was to simply take last year’s games, subtract the first 3 games stats from the total stats. Then Divide that number by 13 to get the average of the last 13 games. Then multiply those numbers by 16 to account for a full season. And Yardage wise, I'm proud to announce our Texans would have finished 13th overall in total yards, 14th overall in Rushing yards and an astonishing 11th in passing yards. If only it were that simple.

In some areas of the country, yards do count in the outcome of the game. Certain states will award a win to a team if after an overtime period teams are still tied, they count trips inside the 20 yard line and then total yards to determine the winner of a playoff game. Alas that is H.S. football. In the rest of the football world, the object of the defense is to keep the other team from scoring and if possible score themselves. Since for the most part defensive scores are an anomaly (with a few exceptions) they don’t really figure into the quality of the defense (despite what any fantasy football player would tell you) we will disregard them for this discussion. Points can’t be that determining factor either though. That is because the defense doesn’t play in a vacuum. Some offenses have a tendency to put defenses in a bad situation, or leave them on the field forever. So if you can’t look at yards and you can’t look at points, what can you possibly look at to give you an accurate measure of a defense?

It was no surprise to me that total yards = points. Mathematically that’s easy to prove. That’s probably why it’s not the most useful stat to break down defenses with. But if you split up yards by total rushing yards and total passing yards rushing yards figure into the equation much more heavily than passing yards, in fact Passing yards is around the threshold of the critical value of r – meaning it just barely meets the criteria for a correlation. That is because unlike rushing (in which a failed carry results in negative, or 0 yards) a failed pass attempt doesn’t really show up in the passing yardage. It’s just not a very effective way to measure passing effectiveness (or pass defense effectiveness).

This leaves you with yardage. What do you consider? Total yardage? That doesn't make much sense to me. Especially considering that the Ravens had almost 15% fewer plays on defense than the Titans did. I think that leaves you with yards per play. But I had to look to make sure there was a statistical significance between yan yards per play and points. So here is what I did. I took several major categories and from each team for the 06 season and compared them to points against. I then took the correlation coefficient and ranked them to attain the most relevant statistics. Here is a look at what each of the following statistics tells us and its correlation coefficient:

(note. The closer the number to 0 the lower the correlation. )


Total Yards ( .757) - This obviously has a high correlation to points. But like points it really doesn’t tell us much. Because total yardage is divided into two separate categories and doesn’t measure the importance of run versus pass defense, nor does it tell us what components of each respective aspect of the game are most important. It’s not a bad way to rank total defense but doesn’t account for those defenses that give up a lot of yards while not giving up many points.

Rush yards allowed (.549) /Pass yards allowed (.332) – The odd thing about this is that passing yards had such a low statistical significance. As a sub discussion of total yards they are helpful, but given the difference in plays from scrimmage on one side of the ball or another which isn’t accounted for, they may not be much help either.

Yards / Play (rushing and passing combined) (.772) – This was slightly higher than just total yardage. It tells you on each play what a defense yields. It will tell you, overall how the defense faired. What it won’t tell you is how the run defense faired or how the pass defense faired. It is very similar to total yards in that aspect but it also accounts for the fact that some teams had 800 something plays while others had over 1000.

Yards per Carry (.506) – I split this up from Yards per pass for a reason. It is kind of like the inverse of the whole completion % problem. Teams that allow a team to run the ball for say 3.4 yards, if they give up more rushes will actually stay on the field longer than a team who gives up 4.4 ypc. The whole 3 yards and a cloud of dust, take time off the clock phenomenon may be playing tricks with the numbers here.

Yards per Pass Attempt (.612) – Think of these as the WHIP of football. Statistically almost as significant as total yards by themselves they give you a better idea of what a team does on a per play basis. Ideally you would be able to split them up to where they happen but that involves a ton of work just to collect the numbers. Because yards/catch is so similar among teams Yards/Pass attempt winds up with an almost identical number to comp%.

Comp% (.615) is a little different number. But every bit as valid. Maybe more so. Most teams in the league will rank about the same in completion percentage that they would YPA since most teams are with in 2.5 yards per reception. Completion % though was a huge difference.

There will always be people who rank defenses differently. It is an inherently subjective ranking. You can argue that injuries, or a few bad games, or a few good games will skew the numbers. Between eras it becomes even more difficult. With the passing game having evolved as it has over the last 50 years more plays get run in a game. If you were going to ask me to use two barometers to to rank defenses within a certain year (2006 specifically) I would use the rushing yards against and completion% against numbers. They are specific enough to tell you something about the two different aspects of the defense while being broad enough to be categorized. An example of a stat that doesn't do that would be the yards per catch against. It doesn't take into account the completion% which since each team has a pretty close yards per completion average, is a stat that definitely figures into the effectiveness of any passing game.

I haven’t run the numbers yet to see where the Texans stand in those categories (to eliminate bias when I finally answer the question) but I will in the morning and then I’ll finally answer the question I started out trying to answer.

Mike

gtexan02
02-06-2009, 08:36 AM
I hear what everyone is saying, but I don't know that I really think we need to look at QB hurries, and heres why:

The beauty of statistics is that we can look at a very large number of occurences, and, in effect, sort of minimize the importance of outlying values. As a result, I think sacks serve basically the same purpose as QB hurries/knockdowns.

If you're looking at one game, you might have a team that knocks the QB down six times, but never actually sacks him. If you look at the next game, that same team might make it to the QB only 3 times, but might sack him every single time. Based on the law of averages, you would expect that if you look at a large enough population, this would even itself out.

A team that gets into the backfield a lot (i.e. has a good pass rush) is going to get more sacks throughout a 16 game season (and especially over a 5 year period) then a team with a poor pass rush. We don't need to know the number of QB hurries/knockdowns, because I think it would be very easy to see that QB hurries and sacks are highly related.


I also see your point about swimwear and bathing suits. But the argument that I was specifically addressing was the following: Does a more active pass rush generate more interceptions?

There are a lot of things that go together in this, but my point was to disprove that a really good pass rush by your front 4 will automatically result in better play by your secondary (in terms of getting INTs)

The Texans have always had a poor pass rush. And we've usually been in the bottom half or worse in takeaways. We get our fair share of fumbles, but we rarely snag many interceptions. The reason given was that our pass rush allows the QB so much time to throw the ball, that our DBs simply can't cover long enough.

If you watch games, you'll see that this is true in many instances. Sometimes our pass rush is so awful that an opposing QB really can pick us apart. But the general trend seems to indicate that turnover oriented defensive backs are much more important than a strong pass rush. This leads me to believe that many INTs are not the result of poor decisions by the QB, but good moves by the defensive backs.

Having a strong pass rush probably results in 3-5 more turnovers over the course of a year. But a team that gets 30 INTs in a season does so because of its secondary. Not its front four.

Teams like Dallas and Cincinnatti of a few years ago prove this point pretty effectively. Dallas had 60+ sacks this season, and single digit INTs. Id be willing to be they led the league in QB hurries as well. Cincinnati a few years ago had 31 INTs but was almost dead last in sacks. I'd be willing to bet they were pretty low on QB hurries as well

Joe Texan
02-06-2009, 04:16 PM
Sacks might hurry a throw but you have to have the hands to catch that throw. Reeves started coming to work but the rest of our guys need some serious training.

When you put a Mario on the feild with a Palalomu(sp) you are bound to come up with fantastic results


I hope Dunta is fully recovered and hits like he used to.

76Texan
02-06-2009, 07:08 PM
Good readings!

Bulluck53
02-06-2009, 09:56 PM
Well lets put it like this, take away the Titans pass rush and Hope doesn't make the Pro Bowl. Probably Griffin as well, I think Finny would still have made it.

leebigeztx
02-10-2009, 09:44 PM
You have to marry everything together. Pressure leads to picks and coverage leads to sacks is the general rule. Another thing yu have to do is match it up with the offense. A good offensive that scores points put the pressure on the other team. So a team like the cardinals, some of their defensive stats are skewed. Teams will go away from the run game and starts to pass which means the dc can dial up the blitz.

gtexan02
02-10-2009, 09:48 PM
You have to marry everything together. Pressure leads to picks and coverage leads to sacks is the general rule. Another thing yu have to do is match it up with the offense. A good offensive that scores points put the pressure on the other team. So a team like the cardinals, some of their defensive stats are skewed. Teams will go away from the run game and starts to pass which means the dc can dial up the blitz.

Thats the point of this thread. Does pressure really lead to picks? How does a team get 60+ sacks and only 8 INTs during the year? The stats don't hold up when you really look at it. Good DBs lead to picks.

leebigeztx
02-10-2009, 10:10 PM
Sacks doesn't mean they were getting consistent pressure. A team like the cowboys this season had guys that go there for the sack, but they had inconsistent pressure. I do believe the tight windows lead to ints. If you watch Baltimore or even TB, their lb's really squeeze the windows. LB's are huge in coverage because they have to cover the middle of the field and the flats . The year the ravens had that great d, they only ha 35 sacks, but they generated a lot of pressure. I don't know the qb knock downs , but pressure is more than just sacks.

gtexan02
02-10-2009, 10:14 PM
Sacks doesn't mean they were getting consistent pressure. A team like the cowboys this season had guys that go there for the sack, but they had inconsistent pressure. I do believe the tight windows lead to ints. If you watch Baltimore or even TB, their lb's really squeeze the windows. LB's are huge in coverage because they have to cover the middle of the field and the flats . The year the ravens had that great d, they only ha 35 sacks, but they generated a lot of pressure. I don't know the qb knock downs , but pressure is more than just sacks.

You're right that pressure doesn't always equate to a sack. But when you look at an entire season, vs one game, I think the two become much closer. A team that consistently gets good pressure is going to get more sacks than a team that doesn't. The odds are just in there favor. If you only get 2-3 chances a game to get a sack, you'll liekly end up with fewer than a team that gets 5-6 chances per game. Part of it depends on personnel, but part of getting sacks is just making opportunities. I don't know I really believe that the Cowboys had inconsistent pressure this season. I bet if it was available, the knockdowns/hurries for the Cowboys would be tops or close to it in the league as well

beerlover
02-15-2009, 12:58 AM
is this a coy attempt to answear the question should the Texans resign Dunta Robinson or draft a CB over a DE? which ever direction they choose it will tilt the strength of talent. why not just compromise & go LB that way you get coverage/int with sacks/pass rush?

Past six winners of NFL defensive rookie of the year

2003 - Terrell Suggs
2004 - Jonathan Vilma
2005 - Shawne Merriman
2006 - DeMeco Ryans
2007 - Patrick Willis
2008 - Jerod Mayo

gtexan02
09-28-2012, 01:04 AM
I know this is an old thread, and there was some controversial aspects to it, but I thought I'd revive it anyway!

I've been doing some more correlations for fun with a friend, and came across this idea again. Here is how it shaped up for last season (2011):

1. No significant correlation between Sacks and QB Rating - R value of -0.1 and a P value of 0.5. A negative R value means that the trend was actually negative.

2. No significant correlation between Sacks and INTs - R value of -0.1 and a P value of 0.4. Again, a negative trend. Just as the historical data showed.


I'll have to wait a few more weeks to see how the numbers for this season are looking, but there are already some interesting teams. The Bengals, for example, 4th in the NFL with 11 sacks but allowing opposing QBs to a 110 QB Rating. Meanwhile Philly and Atlanta are holding QBs to <60 QB rating while only having 7 sacks.

Anyway, the point was that just because Barwin and Reed and company haven't been racking up the sacks as often as we expect, our pass defense is doing fine.

Our pass defense made a big change when we signed Jonathan Joseph and Daniel Manning. Having a great pass rush helps, but it won't substitute for a stud secondary.

I dont have the ability to look at the impact of JJs freakishly long arms though. I bet that would correlate pretty handily with QB Rating

powda
09-28-2012, 01:31 AM
I think hurries would be a signifigant consideration as well as a defensive backs ability to actually catch the ball. I know i've seen a number of should be interceptions mishandled by the texans secondary this year already.

Good stuff gtex.

gtexan02
09-28-2012, 01:45 AM
I think hurries would be a signifigant consideration as well as a defensive backs ability to actually catch the ball. I know i've seen a number of should be interceptions mishandled by the texans secondary this year already.

Good stuff gtex.

If someone could tell me where to find QB hits or QB hurries I would certainly love to look at that.

As for the dropped INTs, man, isn't that true. Especially against Peyton.
I also remember a few years ago when we had Will Demps and his giant cast he had trouble catching balls but could still bat them down

infantrycak
09-28-2012, 03:23 AM
1. No significant correlation between Sacks and QB Rating - R value of -0.1 and a P value of 0.5. A negative R value means that the trend was actually negative.

Are you sure about this one? - it doesn't pass the eyeball test looking at the stats for this year. Comparing the top 16 (lowest QB rating) with the bottom, the top 16 have 4 of the 5 double digit sack teams and all three of the 9 sack teams. The only 8 sack team is at #17. Four 7 sack teams are divided evenly with 4 each. Like I said, I am just eyeballing it and when 7 of the top 8 sack teams are in the top 16 on QB rating and the next 9 are a wash almost making it 11 of the top 16 sack teams are in the top 16 for QB rating it seams odd to find no correlation.

gtexan02
09-28-2012, 11:15 AM
Are you sure about this one? - it doesn't pass the eyeball test looking at the stats for this year. Comparing the top 16 (lowest QB rating) with the bottom, the top 16 have 4 of the 5 double digit sack teams and all three of the 9 sack teams. The only 8 sack team is at #17. Four 7 sack teams are divided evenly with 4 each. Like I said, I am just eyeballing it and when 7 of the top 8 sack teams are in the top 16 on QB rating and the next 9 are a wash almost making it 11 of the top 16 sack teams are in the top 16 for QB rating it seams odd to find no correlation.

Yeah, no significance to the correlation. But its close for this year. Sacks are a relatively rare event, and so the numbers for this season probably aren't very meaningful. Over the course of an entire year they will likely even out. A team like Seattle had 8 sacks in 1 half last week. Events like that skew the results.

Also, I was incorrect in my explanation of the trend. (Probably shouldn't be posting at 2am haha). Anyway, a negative correlation is the expected outcome. More sacks should result in a lower QB rating, so a negative trend would be what you would expect. A positive trend (more sacks = higher QB rating would have been the surprise). Anyway, the correlation was still pretty weak. Heres the data breakdown:

Here is the 2011 data. One point per team. A big reason there was no statistical significance to this is probably because of the Minnesota Vikings. They had 50 sacks last season (good for 1st in the NFL) . However opposing QBs managed a 107 QB rating against them (good for last in the NFL).
http://imageshack.us/a/img402/7241/graph1i.jpg

Here is the data from 2012. More of a trend here, but not "statistically significant." Probably too early to make determinations. Will update later. Remember that when I did this analysis originally there wasn't a lack of connection between sacks and QB rating, only sacks and INTs. But I think the point remains-- a good pash rush can't, by itself, fix a weak secondary. Teams can scheme around a good pash (or a good secondary, but thats a different story) with things like quick slants, 3 step drops, etc.
http://imageshack.us/a/img546/5424/graph2s.jpg

Here is an example of a statistically significant correlation. This is from last year. Teams with high QB Rating tended to win more games. If there were any doubts that this is a passing dominated league, there was almost zero correlation between rush yards per game and wins.
http://imageshack.us/a/img21/2467/graph3y.jpg

The Pencil Neck
09-28-2012, 11:24 AM
Graph QB Rating differential (Team's QB Rating - Opponent's QB Rating) against wins. That should be interesting and probably even a stronger relation.

gtexan02
09-28-2012, 11:32 AM
Graph QB Rating differential (Team's QB Rating - Opponent's QB Rating) against wins. That should be interesting and probably even a stronger relation.

http://imageshack.us/a/img801/1918/graph4.jpg

R value of almost 0.9 (stdev of 1.5). Thats an incredible correlation. Good idea

Heres the fit equation:
y = 0.17x + 8.12 where y is the number of wins and x is the qb rating differential.

If we assume our offense and defense play the same way throughout the rest of the year, we are currently playing like a 14 win team (on the 2011 scale). Of course there is likely to be some regression toward the mean for Schaub (Career passer rating of 92, never been above 98, currently at 102) and possibly for our defense as well once we start playing better QBs. Last year our defense held opposing QBs to 69 passer rating. So if we assume that Schaub stays healthy and has about a 96 passer rating (very reasonable) and our defense regresses a little towards 75 (very reasonable) we are still looking at 11 - 12+ win range

Texanmike02
09-28-2012, 12:23 PM
If you want to do this right take 2 or 3 years, give them a pass rush and a int score then find the correlation coefficient. (excel function between the two lists). You really need to eliminate outliers but that is a little more difficult.

But even if you find a strong coorelation, remember that coorelation does not prove causality. The example I always use is that in the summer people wear shorts more often. People also buy more ice cream cones. If you went back by 2 years you would might get a coorelation of over .90. That does not mean that eating ice cream causes people to want to wear shorts or that wearing shorts makes someone want to eat ice cream.

The point of this is that you can argue that a good pass rush creates interceptions but the opposite might be true. A good secondary can give pass rushers a chance to get to the QB by covering WRs longer. There are other factors in play too. Some teams may have great cover guys who can't catch. They might also have a monster pass rush and guys that can't catch. Good pass rushes might also disuade teams from passing as much. There are so many variables that you really have to look beyond two rankings to find your answer.

edit: was replying to the first post, didn't realize it has been around for 3 years. The first is still a good look but doesn't apply as much because you did more work. The part about coorelation and causality still applies. Also went back and read my rather long def rankings post. I wish I had time to do that stuff today.

Mike

Dutchrudder
09-28-2012, 02:04 PM
Can you make it to where instead of dots, it has the team logos? That would be pretty sweet... :D