At 31, Adrian Peterson trying to do what few RBs have done

Adrian Peterson rushed for an NFL-best 1,485 yards last season, but few running backs have accomplished such a feat at age 31 and beyond. Tom Dahlin/Getty Images

MINNEAPOLIS -- At this time last year, as Adrian Peterson was celebrating his 30th birthday with a lavish party at his home outside Houston, intrigue and uncertainty swirled around the running back's prospects for his ninth NFL season. Peterson had yet to be reinstated from his suspension, return to the Minnesota Vikings or prove he could still be the NFL's best running back at age 30, which is why his league-leading 1,485-yard campaign last season felt like a repudiation of his doubters.

Statistically, though, it would be markedly more impressive for Peterson to reach that rushing total again this fall than it was for him to do it at age 30. There's most certainly a cliff for running backs after age 29; in NFL history, 58 running backs have surpassed 1,000 yards at age 28, and while the number drops to 46 at age 29, it declines by almost half every year after that -- to 24 at age 30, 12 at age 31, six at age 32, two at age 33 and only three at all ages over that.

So while Peterson's 2015 output was extraordinary -- he became the first 30-something rushing champion since Curtis Martin in 2004 and posted the fifth-most yards by a 30-yard-old back in NFL history -- he'll be looking to beat even longer odds in his follow-up season.

Peterson, who turned 31 on Monday, often said he thought there was too much fuss about him turning 30 last season, adding that he doesn't believe the rules about age apply to him. The longer he defies them, though, the more remarkable his achievements will be. If Peterson reproduces his 1,485-yard season in 2016, he'd have the fourth-best season in NFL history at that age, behind Martin (1,697 yards in 2004), Tiki Barber (1,662 yards in 2006) and Walter Payton (1,551 yards in 1985). Peterson wouldn't even have to surpass 1,200 yards to have one of the 10 best age-31 season of all time: Warrick Dunn's 1,140 yards in 2006 currently ranks 10th.

The Vikings have added reinforcements for their offensive line in Alex Boone and Andre Smith, and they're moving back indoors to U.S. Bank Stadium, so Peterson will again be playing in his preferred climate-controlled environment at home. Considering what Peterson did behind a patchwork offensive line last season -- some in the organization regarded it as a minor miracle the running back was able to accomplish so much -- the changes could make yards a little easier to come by next year. Peterson's before-contact average of 2.62 yards was the second highest of his career, according to ESPN Stats & Information, but there were also 10 running backs who logged at least 100 carries and gained more ground before they were hit.

The real test might be in how the Vikings use Peterson next season; he's said he wants to be more versatile in 2016, and coach Mike Zimmer said after the season that he thinks Peterson can do a better job in the shotgun. If the Vikings are headed toward an offense that requires Peterson to operate in the orbit of Teddy Bridgewater, rather than the other way around, it could mean the running back has to be successful outside of his preferred I-formation set. It could also lead to fewer carries than the league-leading 327 attempts Peterson logged in 2015: The Vikings have talked about wanting to convert some of Peterson's carries to catches, and if they're finally successful in doing that next season (either with Peterson or Jerick McKinnon), Peterson's statistics will look different. It's probably not ideal for the Vikings to hand the ball to one running back that much -- indeed, only three 31-year-olds have ever carried it 327 times in a season -- but from the pure perspective of Peterson's rushing totals, a changing role with the Vikings might be the most significant reason his numbers could look different at 31.

Then again, a more balanced attack and sturdier offensive front -- if, indeed, the Vikings are able to establish those things -- could have Peterson running at a higher octane in 2016 than he did in 2015. And the $7 million guarantee in Peterson's 2016 base salary suggests he'll again have a headlining role in the Vikings' offense. It's generally inadvisable to bet against Peterson on a football field, and it could prove to be so again next season.