I think a lot of it has to do with the run game, particularly Foster. Of Foster's 14 carries in this game 11 of them were 3 yards or less, and this has been a trend throughout the season. I've broken his carries down before. In the Bill's game, for example, 12 of his 24 carries in that game totaled minus 1 yard. Sure he'll break a few off for 15, 20, 40 or whatever, and in that Bills game his other 12 carries totalled 112 yards, but it's too many minimal gain plays that puts the offense in bad down and distance.
Now, they've been converting. They were in the top 10 in the league coming into this game, but didn't in this one going 4-17 on 3rd down. 2-9 on 3rd and 7 or longer. 9 occasions where it's 3rd and long. Penalties play apart too, but a lot of that is on Foster getting very minimal gain, if any, on a lot of his carries.
I mean, at the end of the day, the numbers look good, the Texans are 6th in the league in rushing, Foster is 4th in the league, but there's just too many 2, 1, 0, minus yard plays on Foster's carries. Almost Barry Sanders-ish - lose yards on 4 carries then bust one for 50. Lose yards on 4 more carries and bust another for 35. That's 10 carries for let's just say 85 yards, an 8.5 average, which looks awesome, but those 85 yards were on 2 carries. He averaged 0 yards on the other 8 carries that was over 5 possesions where you had to punt 4 times because of those minimal gains putting you off schedule.