I was interested in the same thing - I'm a huge fan of Brian Burke of Advanced NFL Stats, and have been trying to locate some good materials regarding these numbers, what averages to expect, when someone has a breakout season vs. an anomalous season, expectations of regression to the mean, etc.
The only problem is this seems fairly well-hidden, and ultimately may be lurking in the bowels of some pay site. I have yet to peruse all the free sites to find this, but have uncovered a reasonable synopsis at www.fantasypros911.com
. They have a reasonably decent free draft guide (it's like 148 Megabytes and takes forever to download - lots of pictures, I guess). On pages 22-23, Mike Podhorzer has summarized some of these statistics, what the league averages are, and expectations for a select few players. It's not exactly what you were asking for, but it IS a start.
Hopefully this helps - by the way, I am in no way affiliated with FantasyPros911, and have no history of using them, so I can't speak to their expertise - so use at your own risk