Why the Minnesota Vikings Should Trade Adrian Peterson

The heart says stay, stay, stay, but the stats say go, go, go.

The Cleveland Browns are geniuses. Okay, so that may be a stretch. Let me rephrase: the Cleveland Browns have made possibly one good decision over the past 10 years. But this one could set the tone for the future of the NFL running back.

In trading Trent Richardson to the Indianapolis Colts for a first-round pick earlier this year, the Browns capitalized on a system that grossly over-emphasizes the value of a good running game. And it's time for the Minnesota Vikings to follow suit and trade Adrian Peterson.

Peterson is a freak in every positive sense of the term. In his 2,097-yard season last year, he averaged six yards per carry, doing so less than a year after undergoing reconstructive knee surgery. He hasn’t scored less than 10 touchdowns in any of his seven seasons. He can make something special happen every time he touches the football.

Why, then, have the Vikings only made the playoffs three times in those seven seasons and won a grand total of one post-season game? It’s the same reason Barry Sanders was limited to the same amount of playoff success: a team’s success is almost entirely dictated by its passing game.

This isn’t some baseless condemnation of Peterson, Sanders or any of the other great running backs over the last 20 years. The statistics agree.

Over the past three seasons, the correlation between a team’s rushing yards per carry and win total is .02103. That is statistically insignificant. However, the correlation between a team’s passing yards per attempt and win total is .64658. There’s your statistical significance, Uncle Charlie.

In case you don’t believe me, want to check my math, or just think I’m an idiot (you’re probably right), you can check out the Google doc where I did the work by clicking here.

A quick note: on that sheet, you’ll also see the correlation between a team’s turnover margin and their number of victories. When I asked on Twitter a few days ago which statistic people thought was most indicative of a team’s success, most of the serious answers were turnover margin. This data would contradict that.

The correlation between turnover margin and win total was .61702, just a hair below the total for passing yards per attempt. These two are almost statistically identical, and one has been cited by color commentators for decades as the all-determining factor of team success.

To see how important a team’s passing yards per attempt is, you need not look any further than this season. The top-six teams in this category (Philadelphia, Seattle, Denver, San Diego, Green Bay and New Orleans) all made the playoffs. Eight of the top-10 teams in the category made it, with the lone exceptions (Chicago and Arizona) both in contention in the final week of the season.

In Peterson’s seven seasons, the Vikings have averaged more than seven yards per attempt only twice. In 2008, the team (led by Tarvaris Jackson and head-bangin’ Gus Frerotte) totaled 7.1 passing yards per attempt and lost in the Wild Card round of the playoffs. In 2009, under Brett Favre, the team went to the NFC Championship game after recording 8.0 yards per attempt in the regular season. Outside of that? Only one playoff appearance, which came in 2012.

Net Expected Points

One flaw with this method of analysis regarding a team’s ground game is that yards per carry isn’t the best metric to evaluate success. Thankfully, the fine folks here at numberFire have a cure for that.

If you’re familiar with the site, you know of the Net Expected Points (NEP) metric. In case you’re not, here’s a brief crash course. Basically, in every situation (1st and 10 at the 34, 3rd and 4 at the 10), there is an expected number of points that a team will score on that drive. A good play (such as a first down) will increase that, and a bad play (such as a turnover) will decrease it. Over the course of the season, the quality offenses will separate themselves from the rest, where a good team will have (for example) 150 Net Expected Points on offense, where as a bad team may have something like a -100 NEP. It’s essentially a measure of a team’s overall offensive effectiveness. Because scoring points is just a wee bit important in the NFL, this metric can help us decide what works and what doesn’t.

This can further be broken down into Net Expected Points on pass plays (PNEP) and Net Expected Points on run plays (RNEP). We will be using these to decide the Adrian Peterson conundrum.

Of the 12 teams that made the playoffs this year, the average Rushing NEP was 15.60. The Vikings finished second in the league in the category at 42.17. (WHOO HOO PLAYOFFS, BOI!)

Just kidding. It’s a Minnesota sports franchise. You should have known it wouldn’t have a happy ending.

The killer for the Vikings was their -31.53 Passing NEP. That’s 128.7 points less than the average playoff team’s PNEP of 97.17. And the lowest PNEP for a playoff team was Kansas City’s 33.15, still 64.68 better than what the three-headed demon spawn named Ponder/Cassel/Freeman put together.

On their way to a playoff berth last year, Minnesota amassed a 10.65 PNEP. This is still pretty putrid (the league average PNEP was 36.26 last year and 31.24 this year), but it was better than the 2013 dumpster fire.

But back to the original argument - the correlation between rushing success and victories as compared to that of passing success. NEP delivers similar results. The correlation between a team’s PNEP and wins in 2013 was .67039; for RNEP, that number dropped to .21151. This means that a team’s passing success is roughly three times more important than their rushing success. In fact, PNEP had a slightly higher correlation than raw, total NEP (.65438).

What does this all mean? The phrase “it’s a passing league” is more than a cliché – it’s the statistical truth. When you add in Peterson’s age and imminent decline in production, it’s a no-brainer.

I’m not saying that Peterson isn’t valuable. His presence makes the passing game better, and you’re going to win games when he has disgusting numbers like he had last year. But his value pales in comparison to that of a quality quarterback and passing game.

If the Vikings can trade Peterson and get a decent return, great. I’d take that without a second of hesitation. Use either that potential pick or the eighth overall pick to try to find your franchise quarterback.

There’s a reason Peyton Manning- and Tom Brady-led teams have missed the playoffs a grand total of three times combined in their careers, while teams with great backs struggle. The Vikings need to recognize this now, get a return on Peterson before his value diminishes even more, and make a return to relevancy by following the blue print set forward by the Cleveland freaking Browns.