Last in a series on NFC North players whose career trajectories put them on a path to consideration for the Pro Football Hall of Fame:
Of the five players profiled in this project, Minnesota Vikings tailback Adrian Peterson might be the most accomplished relative to his career span. And yet his case exemplifies, more than any other, the difficulty of separating yourself as one of the all-time elites at your position.
Peterson has effected one of the most productive starts to a career for any running back in NFL history. And still, he'll probably need to repeat that output to land in the Pro Football Hall of Fame.
As the first two charts show, Peterson rushed for more yards (5,782) in his first four seasons than all but five running backs in NFL history and more touchdowns (52) than all but four. That measure quantifies what we already knew: Peterson has been the best back in the NFL over the past four years. It also gives us some perspective on how the start of his career compares to the best who ever played the game.
But four years of elite play doesn't necessarily qualify a running back for the Hall of Fame, not when players like Emmitt Smith endured for 15 years or Marcus Allen for 16 or Walter Payton for 13. The threshold for Hall of Fame running backs is the ability to sustain near-elite production beyond the short career arcs of most players at the position.
The next chart shows the 13 Hall of Fame running backs whose careers took place mostly in the post-merger era. Eleven eclipsed the 11,000-yard mark, and the two that didn't -- Larry Csonka and Earl Campbell -- were enshrined amid understandable mitigating factors. Csonka was the lead runner for the best team in NFL history, the 1972 Miami Dolphins. Campbell's white-hot career was cut short after 115 games.
Let's say Peterson doubles his current rushing total to get to 11,564 career yards. Currently, there are 18 players who rushed for at least 11,000 yards. Of the seven who aren't in the Hall of Fame, only two are eligible. Curtis Martin (14,101) and Jerome Bettis (13,662 yards) missed out in their first year of eligibility in January, but both seem likely to be elected within a few years.
Of course, it will be no small feat for Peterson to double his total -- and it isn't likely to come in the four years it took him to get this far. Take another look at the first two charts, which illustrate the historical company Peterson has kept early in his career.
Quite simply, running back is a brutal position. Terrell Davis rushed for a stunning 6, 413 yards during his first four seasons with the Denver Broncos. Slowed dramatically by health issues, Davis managed only 1,194 yards during the final four seasons of his career.
Another former Broncos running back, Clinton Portis, rushed for 5,930 yards in his first four seasons and 3,993 in the five seasons since.
It's possible that history will grade Davis and Portis with a "Broncos curve," a reference to the annual success of running backs in the system of former coach Mike Shanahan. Regardless, both had more production in their first four years than Peterson but slipped off that Hall of Fame pace thereafter.
Since the moment he arrived in the NFL, Peterson has drawn comparisons to Campbell, Eric Dickerson and some of the NFL's other all-time great running backs. His production over that stretch, relative to their early career performances, has justified those associations.
But there is a reason why football people caution such early comparisons with Hall of Famers. Even the all-time greats slow down in the second half of their careers. But importantly, they still reel off a number of highly productive seasons after their early explosions.
Dickerson rushed for 6,291 yards over his final seven seasons after opening his career with 6,968 yards in his first four. Jumping ahead, the still-active LaDainian Tomlinson has rushed for 7,505 yards over six seasons after amassing 5,899 yards in his first four.
So let's arbitrarily say Peterson's cumulative production drops by 25 percent over the next four seasons. That means he averages 1,083 yards per season instead of his current 1,445. At that relatively optimistic rate, Peterson would need to play at least five more full seasons to eclipse 11,000 yards and demonstrate the kind of production over time that would give him the Hall of Fame spot he has positioned himself for.
Obviously, voters don't hold fast to the 11,000-yard barrier and have been known to consider mitigating circumstances. Campbell, for example, took a bruising 1,404 carries in his first four seasons. That's an average of 50 more per season than Peterson has taken, and it almost assuredly contributed to Campbell's short career.
It's easy to say that Adrian Peterson just needs to keep on running like Adrian Peterson in order to make the Hall of Fame. The history of running backs suggests he will slow down at some point in the next four years. The question is how much Peterson produces at a lower rate. To me, another five seasons of 75 percent Adrian Peterson should do the trick.
Earlier: Green Bay Packers quarterback Aaron Rodgers has put himself on the path toward Canton. Chicago Bears defensive end Julius Peppers and the Vikings' Jared Allen face stiff competition. Vikings guard Steve Hutchinson has all the credentials. Packers cornerback Charles Woodson is a lock.