2011, Fred Jackson lead the league in YPC among RBs. 2012, he dropped off big time, probably due to injuries.
One thing to note, though. CJ and Jackson both benefited from Chan's play calling, there was a lot of open space for them to run in, most of the time. We'll see how Hackett handles the offense this year.
Yds from scrimmage per game in 2011, Jackson finished second in the league:
http://www.footballdb.com/stats.html?mode=Y&yr=2011&lg=NFL&sort=totgame
2012, CJ finished 6th (5th among RBs):
http://www.footballdb.com/stats.html?mode=Y&yr=2012&lg=NFL&sort=totgame
We're in pretty good hands.