
Tiki Barber recently called Adrian Peterson "
a liability for his team" due to his propensity to fumble. Is that assessment fair? What if Peterson's fumbles really did hurt his team more than his overall performance helps? Peterson himself
admits he has a fumble problem, and he's promised to work on it in the off-season. How many fumbles is too many when it comes to a break-away home-run hitter like Peterson?
I'll look at Peterson's fumbles in three contexts. First, I'll look at his rumble rate, which accounts for how often he's asked to carry the ball. Second, I'll look at how costly his fumbles have been in terms of
Win Probability Added (WPA). And third, I'll look at his fumbles in terms of
Expected Points Added (EPA), which is less sensitive to game situation as WPA.
Aside from his recent fumble problems in the NFC Championship Game, Peterson has committed 4, 9, and 7 regular season fumbles over his three-year career. That's certainly more fumbles than you'd like to see, but keep in mind how often he's asked to carry the ball.
Any fumble is equally likely as any other to result in a turnover or recovery, so I'll start by looking at fumbles rather than fumbles lost. Further, fumble
rate is going to tell us more than total fumbles about a player's proclivity to lose the ball. For RBs, especially guys who get a lot of receptions, it makes sense to consider their total touches, which includes carries and receptions.