A) he's not that injury prone. Other than 2010 he's played seasons of 15, 14, 16 and 15 games. Not counting his rookie year when he wasn't on the roster until midway through the season.

B) nobody is suggesting he carry the ball 300 times. But give him 200 carries and he's a 1000 yard back. That's not much more than he got the ball in 2009 and he was still in fantastic shape for the playoffs and in fact was one of the team's best players throughout the postseason.