Projecting the NFC North: the Minnesota Vikings' Adrian Peterson

2097 rushing yards, 13 total touchdowns, an average of over six yards per carry, and the NFL MVP trophy.

This is a mere sampling of Adrian Peterson's accomplishments from last season. Yet, his greatest triumph in 2012 was forever altering conventional wisdom when it comes to knee ligament injuries.

Before last season, ACL tears (to make no mention of the other major ligament Peterson ruptured) were thought of as career changers or worse, career enders. In 1999, the reigning NFC and AFC rushing crown winners suffered the injury within two weeks of each other. Each was the same age as Peterson when he tore his ACL. Terrell Davis, himself a member of the 2,000 yard club, played only 13 more NFL games while Jamal Anderson managed one more 1,000 yard campaign before fading into oblivion. Each retired three seasons later, both before their 30^th birthday.

Adrian Peterson

See all SBNation coverage of the Vikings' running back here and at The Daily Norseman

Cut to Christmas Eve 2011, the day Peterson ruptured his ACL and MCL. At the moment of the injury, the near-universal assumption about Peterson's upcoming year was a stay on the PUP list with a chance to avoid injured reserve. While he missed all of training camp and the preseason, the Vikings' All-Pro running back returned for week 1. But Peterson wasn't merely returning ahead of the "realistic" expectations; the player known as "Purple Jesus" made a run at history, ultimately falling just eight yards short of Eric Dickerson's single season rushing record. In the process, Peterson changed not only his team's fortunes in 2012, but the perception of ACL tears across the league.

After viewing the litany of Peterson's accomplishments, it's easy to assume another spectacular season is on the horizon. However, as the running back enters his late 20s, and with the wear of 1,754 NFL carries already on his body, Peterson may fall much shorter of his 2,500 yard prediction than most expect.

It's true that we're dealing with a small sample size here, but there will never be a time where 2,000 yard rushers aren't a small sample size. Even if the data pool isn't optimal, approaching the numbers cautiously is better than not approaching them at all.

The track record of tailbacks in the year following a 2,000 yard season suggests that runners wear down quicker and by consequence are more susceptible to injury. The most noticeable trend between these backs is the precipitous drop in efficiency. The lowest average yards per attempt in a 2,000 yard season is Terrell Davis' 5.12. Contrast that figure with 4.35, the highest similar metric in a year after a 2,000 yard campaign, and you begin to see how difficult the year after can be for tailbacks.

But it's not just efficiency that dips. Four running backs gained over 800 fewer total rushing yards the year after, with two seeing 1,000+ yard drop offs. The closest a 2,000 rusher came to repeating the performance was Barry Sanders' 1,491 yard season, and as we'll see Sanders is the anomaly. On average, these backs gained 968.3 fewer yards the season after a 2K output.

Then there's the other concern we touched upon earlier: heightened risk for injury. Half the backs missed games in the season following 2,000 yards. At first, that figure doesn't seem particularly surprising. Running backs are hit virtually every time they touch the ball, and workhorse rushers will often carry the ball 300 or more times a season. What we do know is running backs are more likely to miss games later in their careers, and 2,000-yard rushers tend to be younger backs. Of those players, three were 24 during their 2K year, 2 more were only 26, and the average age was merely 25.7. Runners tend to be more resilient to injury in those years. That half the backs missed multiple games and two suffered ACL tears indicates that serious injury is a greater possibility the year after 2,000.

So what does this mean for Peterson?

What hurts him most is that he's on the very top end of age for not only 2,000 yard rushers, but top tier running backs in general. Of the players in the 2K club, only Sanders was older. It's worth pointing out that Sanders did have the best year after 2,000 yards of any of the backs, and perhaps Peterson too will exceed expectations. However, Sanders was a far different player than Peterson, and the difference probably explains why Sanders had his 2,000 yard season so late in his career. Sanders was famously an undersized back with incredible change of direction. As a result, he rarely absorbed big hits and remained productive his entire career. Peterson on the other hand has endured many more gruesome hits including the one that resulted in his ACL tear. While Peterson managed a 2,000 yard season several years into his career and should be commended for it, the nature of his play makes highly improbable that he'll follow Sanders' path.

Accordingly, I think a fair projection for Peterson in 2013 is somewhere between 1,200 and 1,350 yards at around a 4.4 clip. While that's still in the upper tier of running backs, it's a hefty drop off from 2012. It also means that the Vikings will have to improve significantly in the pass game and on defense in order to return to the postseason.

If Peterson somehow produces anywhere close to his MVP season, many will say "I told you so." Yet, if his play indeed falls off, that too will seem expected. Either way, it'll feel like we should have seen it coming.

Jason Hirschhorn covers the Green Bay Packers for Acme Packing Co. He has previously written for Lombardi Ave, College Hoops Net, LiveBall Sports, and the List Universe. He is also currently a senior writer for Beats Per Minute, an indie-music webzine. Follow him on Twitter: @JBHirschhorn