No one was surprised when the Vikings decided in February to let Adrian Peterson walk instead of paying him $18 million next season. The 2007 first-round pick, long considered the best running back in the NFL, was hampered by a knee injury last season, and at 32, history suggests he's well past his prime.

But by late April, the Saints had signed Peterson to a two-year deal. On the surface, the best-case scenario was that Peterson would be able to spell feature back Mark Ingram. But voluntary workouts have Peterson's new teammates marveling at how much he resembles, well, Adrian Peterson.

"He's a stud, man. He looks the part," Saints quarterback Drew Brees said in early June. "There's something about handing the ball off to that guy and watching him run through the hole and take on anybody who tries to tackle him."

Saints left tackle Terron Armstead added: "I'm amazed, honestly. Seeing him just take off his first few steps are as explosive as I've ever seen by a human being. It's unbelievable. I'm very excited to see him when the pads come on."

And here's Saints safety Kenny Vaccaro: "It's ridiculous. He has not lost any steps. Wait, just watch. He's so explosive ... just in flat shoes out there."

Peterson has said that he feels like he could play till 37 or 38 -- "approaching 40," even -- which brings us back to Vaccaro.

"Like he's not lying, y'all, he's playing til he's 40," Vaccaro said recently. "I'm telling y'all. Y'all about to see like when he tore his knee and came back and ran for 2,000 yards. Now, obviously, we aren't gonna just feed him like that ... but he is gonna be a factor."

Vaccaro's referring to when Peterson tore his ACL in December 2011, rehabbed all offseason and started 16 games in 2012 rushing for 2,097 yards (6.0 YPC) and 12 touchdowns. It was superhuman, even in the finely-tuned world of professional athletics. But now Peterson is 32 and coming off a meniscus injury that sidelined him for three months last season -- and limited him to just 37 carries, a 1.9 yards-per-carry average and zero touchdowns.

Put another way: Can Peterson do what other running backs on the downside of great careers couldn't? Namely: Outrun Father Time?

Before we try to predict the future, let's first look at just how dominant Peterson was for much of his first decade in the league with both conventional stats and Football Outsiders' total-value metric.

  • 2007: 14 games, 1,341 yards, 5.6 YPC, 12 TDs, No. 4 in total value;
  • 2008: 16 games, 1,760 yards, 4.8 YPC, 10 TDs, No. 17 in total value;
  • 2009: 16 games, 1,383 yards, 4.4 YPC, 18 TDs, No. 10 in total value;
  • 2010: 15 games, 1,298 yards, 4.6 YPC, 12 TDs, No. 6 in total value;
  • 2011*: 12 games, 970 yards, 4.7 YPC, 12 TDs, No. 9 in total value;
  • 2012: 16 games, 2,0976 yards, 6.0 YPC, 12 TDs, No. 1 in total value;
  • 2013: 14 games, 1,266 yards, 4.5 YPC, 10 TDs, No. 25 in total value;
  • 2014**: 1 game, 75 yards, 3.6 YPC, 0 TDs;
  • 2015: 16 games, 1,485 yards, 4.5 YPC, 11 TDs, No. 6 in total value;
  • 2016: 3 games, 72 yards, 1.9 YPC, 0 TDs;

* Peterson tore his ACL in a Week 16 game against the Redskins. Seven months later he not only returned to the Vikings' lineup, he finished the 2012 season as the NFL's highest-rated running back.

** Peterson played in just one game before he was suspended for the rest of the season due to a child-abuse case.

Peterson was a top back in 2015 and perhaps he would still be in Minnesota if he hadn't gotten injured last season. But he did, the Vikings moved on and the Saints feel like Peterson can be an integral part of their offense even if he is on the wrong side of 30.

"I'd be lying to you say it doesn't give you a chip (on your shoulder). Especially being a competitor," Peterson said last week, via the New Orleans Advocate's Nick Underhill. "It's not my main focus. It's something that drives you a little bit. After 30, because it was the same back then. 'Oh, he's 30.' Then I ended up leading the league in 2015. Same thing the next year. Stuff will continue to repeat itself until I finish."

Peterson's right, of course, which brings us to our next question: What does history say about when he will be finished?

Let's start with the top-10 running backs from their age-32 season (from 2000-2016):

Ricky Williams2009Dolphins1624111214.6570.111
Emmitt Smith2001Cowboys1426110213.9172.93
Mike Anderson2005Broncos1523910144.2467.612
Frank Gore2015Colts162609673.7260.46
Jerome Bettis2004Steelers152509413.7662.713
DeAngelo Williams2015Steelers162009074.5456.711
Thomas Jones2010Chiefs162458963.66566
Fred Jackson2013Bills162068904.3255.69
Corey Dillon2006Patriots161998124.0850.813
Garrison Hearst200349ers121787684.31643

That's an impressive list that includes three 1,000-yard rushers. Put another way: It's reasonable to think that Peterson could have a Peterson-like season in 2017. But don't expect that productivity to last; here are the top-10 backs from their age-33 season:

Frank Gore2016Colts1626310253.9064.14
Emmitt Smith2002Cowboys162549753.8460.95
Warrick Dunn2008Bucs151867864.2352.42
Ricky Williams2010Dolphins161596734.2342.12
Antowain Smith2005Dains161666593.9741.23
Terry Allen2001Ravens111686583.9259.83
Fred Jackson2014Bills141415253.7237.52
Thomas Jones2011Chiefs161534783.1229.90
Darren Sproles2016Eagles15944384.6629.22
Jerome Bettis2005Steelers121103683.3530.79
DeAngelo Williams2016Steelers9983433.538.14

The numbers are down across the board -- from attempts, to total yards, to yards per carry to touchdowns. And that's to be expected because running back is among the most fungible positions in football; teams can find comparable -- or better -- production from younger, cheaper players.  It's why you don't see high-priced running backs in their 30s littering NFL rosters while the Tom Bradys of the world can still be at the top of their game as a soon-to-be 40-year-old.

Because we're curious -- and because Peterson mentioned that he could see himself playing until he was 38 -- here are the combined season totals for the top running backs, age 34-38:

Emmitt Smith200320042535711933.3447.711235
Ricky Williams20112011161084444.1127.82134
Dorsey Levens2004200415944104.3627.34134
Lorenzo Neal2004200877993483.524.51538
Kimble Anders2000200015763314.3622.12134
Mack Strong2005200737542464.566.61336
Zack Crockett2006200717401634.089.60235
Tony Richardson2005200971351584.512.20538
Fred Taylor201020107431553.622.10134
Larry Centers2002200325321384.315.52235
Priest Holmes200720074461372.9834.30134
Thurman Thomas200020009281364.8615.10134

Notice the right-most column. That's the age these backs -- many of whom were fullbacks and still contributed as blockers -- last played in the NFL. A feature back's existence, in general, burns brightly before flaming out. The good news is that Peterson could have a bounce-back year in '17 and live up to the praise we've heard from his new teammates in recent weeks. But the reality is that, beyond next season, it's more likely than not that Peterson will be just a shell of himself. There is no shame in that because unless you're a franchise quarterback, professional football is a young man's game.

Then again,  Peterson is more than your garden-variety feature back.

"If you can reverse Father Time, maybe he knows him," Saints defensive end Cameron Jordan said recently, via "I don't know, but either way, I'm going to be getting real familiar with A.P. to understand how can I move as he does at the age that he is."