Parkers main deal this year is to hold onto the damn ball. He's got the running between the tackles down alot more than he did 2 years ago and he's learning how and when to use his speed when following his blockers but he's got eat, sleep, and breathe holding onto that football.
Jerome rarely fumbled, but he did on occasion and usually at the worst times; if Willie can have a career where he fumbles as little as Jerome did overall, I'll be quite happy.
Dude there was one year were the Bus did fumble 7 times. I don't remember the year off hand but I do remember he had a year where he had the case of the fumbles. The more experience Willie gains the more he will learn to hold onto the ball.