Why a year? What takes a year to learn & what methods would be used to train him?
I ask, because some will say the best way to learn is on the field.
It doesn't necessarily have to be a year. It's as long as it takes to get him comfortable with the system and his responsibilities. Sometimes that takes a couple months, sometimes it takes a year or two. Depends on the player. It didn't take Luck or Bridgewater long at all. They ran the offense as rookies. They also had tons of experience doing that in college. It took Carr and Bortles a little longer so they ran watered down versions of the offense as rookies. Not surprising considering both had limited experience doing that in college. Personally, I'm not a fan of watering down my offense just so a rookie can run it. But that's just me. That was the only way they could get those guys on the field without being overwhelmed so that's what they went with. To each his own.
For guys with limited experience running a pro offense, I typically aim for a year window because that gives him a season to watch and learn and then a full offseason of going through everything and applying that knowledge that he now has in hand. I would play a guy later in the year if I thought he could go out and not get overwhelmed so he can get his feet wet, but I'm not going to let his draft status impact his development. If he's not ready then he's just going to spend his time on the field confused. He's not going to learn a whole lot and may even regress because he has no idea what to do.
The offseason is the important part. As a rookie, you're just sprinting the whole time to keep up. A player makes his most progression during the offseason after his rookie year because now he has all this knowledge and he can apply it. For a guy who's never run a pro system before, as a rookie he's going to be more worried about his pre-snap obligations, drop steps, and the playbook before he even starts worrying about reading the defense and getting through progressions. If you're on the field and you're more worried about that stuff then you're going to spend much more time just reacting to the defense rather than applying your knowledge and engaging.
For a guy like Goff, who has never run a pro offense, he's going to be learning a ton whether he's on the field or not because the offense and it's concepts are all new to him. Once I feel he's comfortable with those concepts then I will explore him going out and applying them on the field. That takes time though. What all is there to learn you ask?
He's going to have to learn and master the playbook (this means formations, play packages, pre-snap reads/adjusments, etc), he's going to have to learn and master verbiage, he's going to have to learn and master protections, he's going to have to learn and master audibles, he's going to have to learn and master reads, he's going to have to learn and master progressions, and he's going to have to perfect his mechanics. You think that takes months? Just look at Cam Newton. It took 4 years for things to click. But once they do...
Edit: As Texian pointed out above, live reps are great, but if you are overwhelmed then they are not doing much for you. If you can't run the offense then it's better to stand aside and watch someone who can. Then you can gain comfort in the knowledge you are gaining from observing.
It's not that much different than being in a classroom. If you showed up for your first day of physics and the teacher told you to solve the equation on the chalk board you would be like "what, seriously?". But if the teacher showed you the formula for the equation and the process of how to solve it and then asked you to do it you would feel so much more comfortable in doing so. Comfort is a key ingredient to a player's development that is often overlooked. Just look at Robert Griffin. You think he was comfortable during his development years? He spent the entire time either injured or in the dog house. Not exactly the best learning environment.
