Adrian Peterson had four fumbles as a Vikings rookie in 2007, a reasonable number for someone who touched the ball 257 times from scrimmage.
That jumped to nine fumbles in 2008 and seven more in 2009 — not counting the infamous NFC title game.
Every time the fumbles were talked about as a growing concern, with evidence of that during the 2008 season, they seemed to gain a certain mythology. Peterson insisted he was working on it, and even would carry a football around with him in the locker room as a means of increasing his handle on ball security.