EDEN PRAIRIE, Minn. -- Even before Friday's news that he would be listed as doubtful for the final game of the Minnesota Vikings' 2013 season, this year would have to qualify as a trying one for Adrian Peterson. The reigning NFL MVP began with talk of breaking Eric Dickerson's season rushing record after falling just 8 yards short last year, and his team had aspirations of a deep playoff run after a surprising 10-6 finish in 2012.
Only time will tell whether Peterson's 2013 season was an injury-induced fluke, a regression to the mean or the toll of a heavy workload catching up with him. And it's not like he's had a bad season. Assuming he doesn't play Sunday, Peterson will still, in all likelihood, finish among the league's top five or six rushers, despite carrying just 18 times in the Vikings' final four games. He had a shot at his second straight rushing title despite playing much of the year with nagging hamstring, groin and foot injuries that sapped his breakaway speed and made Peterson, by his own admission, run tentatively at times.
But time won't give Peterson -- or the Vikings -- this year back, and by the next time he steps onto a football field, he'll be 29 years old, gearing up for the first of two seasons outdoors. The Vikings' next indoor home game will come when Peterson is 31 years old in 2016. In light of all that, it's not hard to feel a lingering sense that Peterson's time as an elite running back might be slipping away.
History certainly doesn't play in his favor. Peterson has run for at least 1,300 yards in four of his seven NFL seasons; since the 1970 AFL-NFL merger, only 11 running backs have run for at least 1,300 in a season. The number of 1,300-yard seasons by a 30-year-old running back drops to nine, and by age 31, it's down to five. Only one running back since the merger -- Walter Payton in 1986 -- has run for more than 1,300 yards at age 32, and Payton is the only one even to eclipse 1,200 yards at that age.
Peterson's 1,266 yards are the 20th-most by a 28-year-old running back, behind lesser lights like William Andrews, Christian Okoye and Terry Allen. None of those players eclipsed 1,300 yards again after their age-28 season, and only Okoye posted another 1,000-yard season.
Peterson has much more in common with thoroughbreds like Emmitt Smith, Barry Sanders and Payton, and all three had seasons between the realms of great and dominant after they hit 29; Smith hit 1,332 yards at 29 and 1,397 at 30, Payton ran for at least 1,300 yards each year from 29 to 32, and Sanders had his MVP-winning, 2,053-yard season at 29 before running for 1,491 at 30 and then calling it quits.
But let's say Peterson can do that. He'll still have to carry a Vikings team that could be breaking in another new quarterback, and he'll have to play the next two seasons outdoors, where he's averaged about a quarter yard less (4.84) a carry in his career than he has indoors (5.08), according to ESPN Stats & Information. The running back has made no secret of his disdain for playing outdoors, and while bad weather might limit passing games, it can also slow down backs looking for big gains.
These numbers won't be popular with Vikings fans -- and probably not with Peterson, who enjoys few things more than excelling in the face of long odds. But Smith, Sanders and Payton enjoyed defying the odds, too, and time eventually caught up with all of them; Payton retired after a 533-yard season at age 33, while Smith never averaged more than four yards a carry after 32.
There's strong statistical evidence that elite seasons by a running back become increasingly rare after the age of 28, and even if Peterson can crank out a few more, the Vikings can't count on him being in a stratosphere of his own for much longer. That they couldn't do more with his age-28 season has to register as a disappointment.