MANKATO, Minn. (AP) — Jim Brown spinning his way through the line and breaking loose in the secondary with a burst of speed.
Walter Payton lowering a stiff arm and tearing away from the tackler with those long, almost-straight-leg strides.
Barry Sanders slithering around in the backfield and finding a seam to dart through.
View some of the best images of Adrian Peterson from the 2013 season.
Those are the enduring images of grit, perseverance and even elegance on which the NFL's multibillion-dollar empire was first built.
These days the workhorses have become a fading breed. Quarterbacks are the unquestioned stars of the modern game.
"We're not getting the ball 30 times or 20-something times a game. Sometimes I get the ball 10 times and the rest of it is catches," Kansas City's Jamaal Charles said. "It's just the way they use me now. The game has changed."
Adrian Peterson nearly broke Eric Dickerson's NFL single-season rushing record in 2012 on his way to winning the league's MVP award for Minnesota. At this rate, though, Peterson could be the last running back to get one. Even he, with that relentless nature and throwback style, has acknowledged an acceptance of the shift in this role.
"I'm trying to win a championship, so if that's taking less of a pounding and being more productive in the pass game, I'm all in for it," Peterson said.
At age 29, Peterson is perhaps the NFL's last great workhorse running back.
Maybe someone a year or two younger like Charles or Seattle's Marshawn Lynch or Philadelphia's LeSean McCoy will pass Peterson on the all-time list and defy the trend with a productive career into his mid-30s. But there are many signs that won't happen:
— For the second straight draft, no running backs were selected in the first round, an absence not seen since 1963. Over the last five years, a total of seven running backs were first-round picks. From 2000-2004, there were 15. From 1985-1989, there were 25.
— Last year, only McCoy and Lynch ran the ball 300 or more times. In 2003, 13 players did that.
— Only nine teams in the league last season had one player take 60 percent or more of their rushing attempts, down from 14 in 2003 and 14 in 1998. Nine teams also had two players with 30 percent or more carries last year, up from five in 2003.
— Last season's leader in team rushing attempt percentage was Chicago's Matt Forte with 72 percent, and he's not close to appearing on an all-time list. According to STATS research, the most recent player in the top 20 was Edgerrin James with 81 percent for Arizona in 2007. Even Peterson has never topped 72 percent in his career. James has the most in history, according to STATS, with 89 percent for Indianapolis in 2000.
— Only two of the last 10 Super Bowl champions have featured a 300-carry running back: Lynch last season and Corey Dillon for New England in 2004-05. The New York Giants finished last in the league in rushing in 2011 and still went on to win the title.
So how in the name of Emmitt Smith did the game get to this point?
With players bigger, faster and stronger, the guys running the ball now are simply more prone to getting beat up than their predecessors from the previous generations.
Teams must constantly develop replacements not only for down the road when the featured runner turns 30 but for in-game breaks to keep him fresh. The committee approach can also help prevent the defense from getting too comfortable with one particular style. The evolution of the passing game, with Charles and the Chiefs as an example, has also essentially transformed several running plays per game into short throws.
Thus, teams have a hard time justifying paying running backs as their franchise players. Peterson is the outlier with a salary cap hit this year of more than $14 million. The next-closest running back is McCoy at $9.7 million. The money has been shifting not only toward the quarterbacks, but also the guys paid to protect them or catch their spirals. Even the guys that try to sack quarterbacks and intercept passes are making more than running backs.
The Seahawks were champions with Lynch as a bruising old-school running back, and San Francisco has been one of the league's best teams lately with a similar approach behind Frank Gore. Those teams also feature quarterbacks with exceptional running ability and the read option as a staple of their playbooks. The way they move the ball is far different than when the Bears used to build their offense around Payton.
Fundamental changes have taken place. The NFL might not ever see another 400-carry running back. But maybe it's wise.
"If you're looking at what's going on here lately you'd think it's been devalued a little bit, just from a numbers standpoint and money-wise, too. But you always hear the league's kind of cyclical," Vikings fullback Jerome Felton said. "I think if you look at teams that are successful, they do run the football. There's only so many Tom Bradys. There's only so many Peyton Mannings. So unless you have one of those guys, it's important to be able to run."