Will Adrian Peterson Fade in the Fantasy Football Playoffs?

Like Marty McFly in Back to the Future, might Adrian Peterson fade away in the last few weeks?

Nearly everyone is familiar with the lore of the 1989  Back to the Future, Part II, which famously predicted that the Chicago Cubs would win Major League Baseball’s World Series in 2015 (and they nearly did). Still, the original Back to the Future was an even more exciting and timeless romp through history.

Teenager Marty McFly accidentally goes back from his present 1985 to 1955 in a modified time-traveling car. His presence in the past, however, throws off the events of the original timeline, including the fact that his parents almost never meet. Marty himself begins to fade from a picture of his family that he kept with him, and he has to set his parents up together (and get them to... you know) to ensure his own future existence.

Talk about an awkward family tree.

Adrian Peterson of the Minnesota Vikings may not have a plutonium-powered car to help him, but he’s seemingly defied time as well this year. 2015 marks his ninth year in the National Football League, and he seems to still be able to hit 1.21 gigawatts even in his age-30 season. Still, while Peterson’s 1,164 rushing yards through Week 12 lead the NFL, he’s put up less than 4.0 yards per carry in three games this year.

Can Peterson stay vintage through the end of the season, or will he fade away from our fantasy playoff pictures?

This Is Heavy

The way Peterson glides through a defense is a lot like watching Marty McFly skitch a truck while on a hoverboard: even this far into his “future”, he can bend corners with ease, blast through a pile of bullies, and elude tacklers from every direction.

He’s been able to sustain this level of play while opposing defenses are stacking the box against him -- refusing to wait back and respect the passing game under quarterback Teddy Bridgewater -- and with an offensive line that has weathered injury and ineffectiveness all over. Left tackle Matt Kalil has been a trainwreck in blocking the past few years, and starting right tackle Phil Loadholt suffered a season-ending torn Achilles’ in preseason. Fortunately for fantasy teams, Peterson has been able to carry his Vikings yet again; per Pro Football Focus, his 2.5 Yards After Contact per Rush ties for 19th out of 70 running backs with at least 25 percent of their team’s rushing snaps in 2015.

I wrote a few weeks ago about how legitimate the Vikings’ playoff chances are, and Peterson is a big reason why they’ve gotten this far. Still, can he see them -- and us -- through to the end of the season?

Save the Clock Tower

As we come into Week 13, some fantasy playoffs are beginning and others are just one short week away. We need to know if Peterson can be the player to sustain our fantasy teams into an extended December postseason run. He’s gotten off to a pretty good start, with a turkey-fueled 158 rushing yards and 2 touchdowns on 29 attempts in Week 12, but how sustainable is that?

We can turn to numberFire’s signature metric, Net Expected Points (NEP) to figure this out. NEP helps us take the numbers we get from the box score and assign them contextual value so they relate even closer to the game on the field. By adding down-and-distance value, we can see just how much each play and each team as a whole influence the outcome of games. For more info on NEP, check out our glossary.

The table below (or this graph) shows Peterson’s 2015 weekly production in terms of half-PPR scoring fantasy point output (green line) and weekly Rushing NEP change (blue line). This is matched up against the current rank of his opponents in Adjusted Defensive Rushing NEP per play (red line); the higher the rank in this, the easier the matchup. By checking this, we can compare how well he’s performed in both tough and easy matchups.

Week FPTS Rush NEP +/- Opponent (Rank)
1 6.7 -0.90 SF (28th)
2 18.2 -4.55 DET (21st)
3 24.6 +6.21 SD (32nd)
4 17.4 +0.97 DEN (11th)
6 6.2 -5.15 KC (7th)
7 12.5 -1.31 DET (21st)
8 11.9 +1.66 CHI (30th)
9 21.3 +0.04 STL (2nd)
10 28.6 +8.99 OAK (27th)
11 11.1 -4.07 GB (25th)
12 31.7 +6.74 ATL (6th)

Remember as you look at this, that since rushing the ball is inherently less efficient at accruing expected points than receiving, an average running back performance in a week will be negative. Anything near zero or positive is a pretty impressive showing.

Of the five bottom-10 matchups he’s had, Peterson has posted positive Rushing NEP three times (and near-zero a fourth). Of the three top-10 matchups he’s faced, he’s put up two positive Rushing NEP games. We can see this as -- in most weeks -- Peterson’s Rushing NEP rises in sync with his opponents' rank in preventing the rush. The only weeks it isn’t perfectly on are weeks where he outperformed the matchup (versus Atlanta and even Denver) or in divisional matchups, where it appears he was schemed out of the Vikings’ gameplan.

In addition, the only weeks that saw Peterson with fewer than 10 fantasy points came in Week 1 (weird play-calling worked against him) and the team’s Week 6 tilt (when he faced the seventh-ranked Chiefs). The only other weeks he didn’t outperform his opposition were divisional matchups, again showing signs of vulnerability to game planning. Peterson doesn't appear to be "matchup-proof" like earlier versions of himself, but he is clearly very good when the matchup is right and can go off even on an unsuspecting top-tier run defense, due to the volume of touches the Vikings are willing to feed him.

Great Scott!

Based on the above data, it seems the pattern with AP is to perform in sync with expectations in Rushing NEP; if it’s an easy defense, he’ll do well, and if they’re tough, he won’t. In fantasy, however, he’s underperformed to NFC North teams (likely due to their annual exposure to, and knowledge of, him) and obliterated top-tier defenses like the Atlanta Falcons, St. Louis Rams, and Denver Broncos. He’s got a ton of upside no matter the occasion but seems to be susceptible to division rivals.

With this in mind, can we predict the rest of the fantasy season for Peterson?

The table below shows his remaining opponents, as well as their Adjusted Defensive Rushing NEP per play totals and ranks. Can AP finish the year on top?

Week Opponent Adj. D RNEP/P Rank
13 SEA -0.07 4th
14 ARZ -0.06 8th
15 CHI 0.08 30th
16 NYG 0.00 16th

When one looks at this table, it looks pretty darn tough for the next two weeks and tasty for the later fantasy playoffs. As we know, though, he goes big against top-10 units and folds against divisional rivals, so we might have to look at this differently. If we consider likely game scripts as an indicator of how Peterson will perform, against two top-10 units in numberFire’s pass defense metrics (Seattle and Arizona), he’ll likely get to run the ball a lot as the Vikings attempt to control the game.

Against the bottom-10 passing defense of the Chicago Bears, quarterback Teddy Bridgewater may get to test his arm a bit more. In a neutral matchup against the New York Giants, the offense should run through Peterson like usual.

Even going into these next two brutal weeks, our algorithms project Peterson as the top running back in fantasy for the rest of the season: he should have 104 rushing attempts for 466 yards and 3.4 touchdowns, 14 receptions for 93 yards, and around 83.57 more fantasy points.

You’ve trusted AP to get you this far; don’t stop now. Buckle in and watch him continue to warp time and space for your fantasy squads in 2015.