Knowing how much Coach Mangini hates turnovers on offense, it must be damn hard for him to digest that it is not possible to coach emerging star fullback Peyton Hillis out of his fumbling. I've read that each week Hillis does special drills designed to get him to hang onto the ball and no matter the effort, every week Hillis coughs up a ball. I've often compared Colt McCoy to Brian Sipe, in the case of Hillis there is another reference point in Browns history that is very similar. Mike Pruitt ran like a linebacker but he also had smallish hands and often fumbled. Forrest Gregg hated Pruitt's fumbling so much that he sat him for the better part of two years. When Sam Rutigliano arrived, he decided to put this force of nature into motion and Mike Pruitt was a key part of the Browns resurgence.
It's the same story with Hillis. 250 pound players with speed and agility are rare. Keep giving him the ball, his one fumble per game is more than offset by the damage to opponents that he does on the ground on all the other plays in which he doesn't fumble.