By Brian Burke
Adrian Peterson is currently the highest paid RB who is due to make $11 million this season, which is probably two to three times too much. RBs, and the running game in general, do not have the impact on wins and losses the same way the passing game does. But more importantly, the spread between the best and the mediocre RBs is much smaller than the the spread among quarterbacks.
We can't quantify the value of a player the way the MLB analysts can, with Wins Above Replacement and other stats. But we can at least make some back-of-the-envelope, order-of-magnitude estimates.
Comparing the standard deviation of 2010's top 40 QBs' stats to the top 40 RBs' stats shows that the difference between winning and losing rests far more in the QBs' hands. The SD of QB WPA is 1.75 wins, and the SD of RB WPA is 0.47 wins, a factor of over 3 in favor of QBs. On a per game basis, it's a factor of over 4.2.
Comparing EPA, the SD for QBs is 58 points, and the SD for RBs is 18 points. That's a factor of over 3 in favor of QBs. On a per play basis, it's a factor of 1.4 in favor of QBs, but keep in mind that top QBs are involved in twice as many plays as the top RBs.
But when it comes to running stats, it's Success Rate and not EPA or yards that matter in winning games. Chris Johnson's career SR is only 38.2%, compared to the average SR of 38.6% for all RBs. Johnson is a homerun hitter, and although that's what makes it on Red Zone Channel, it's not necessarily what wins games. It's the steady threat of 4- or 5-yard gains that opens up the passing game, not the occasional break-away TD run that makes a winner. It doesn't matter that you hit 50 HRs when you strike out on 62% of your at-bats.
Johnson does have impressive Yards Per Carry numbers for his career. 5.0 YPC is solidly above average. But much of that is thanks to his one amazing season in 2009. Last year, his average was down to 4.3, nearly average. In 2010, his WPA was -1.0 wins and his EPA was -33 points (yes, solidly negative). For his 3-year career his total WPA is only 0.40 wins, or 0.13 wins per year. In simple terms, that means adding the Chris Johnson running game to an otherwise completely average team would make it...a completely average team.
RBs in general are known as injury risks. Plus, Johnson isn't exactly known for his pass blocking. Both factors weigh against giving him a giant contract.
This isn't a knock on Johnson as much as it is on how RBs are overvalued in the NFL. I think there are a several reasons why this continues. A few decades ago, the NFL was truly a running league, and great RBs could make a much bigger impact on the game. There's also the illusion from the fact that RBs happen to be the guys with the ball in their hands and the stats on the back of their trading cards. We all remember the days on the sandlot or on the varsity team where RB is almost always the best athlete on the field. Lastly, there's the age-old causation/correlation fallacy in which RBs on winning teams pad their yardage totals sealing wins in the 4th quarter, making RBs appear to be causing his team's success.
An accountant might be able to make the case that Johnson is worth more than the wins he can generate because he puts butts in seats and jerseys on backs. But you know what else sells tickets and jerseys? Winning. Take the $12 million per year, put it into your offensive line, and draft a couple 4th round RBs. You'll thank me later.