If there is one peer that Adrian Peterson considers his closest rival and the guy he really, really, REALLY wants to top, it would no doubt be Chris Johnson.

Peterson has never come out and said that. But anyone who has interviewed him since 2009 knows this to be the case.

When the 2009 season began, Peterson was, well, Peterson. In the eighth game of his 2007 rookie season, he ran for a league-record 296 yards. In his second season, he ran for a Vikings franchise-record 1,760 yards.

Johnson, who joined the league a year later than Peterson, was a 1,200-yard rusher as a 2008 rookie. Good, but no Peterson.

In 2009, however, things began to change, at least temporarily. For the first time in his three seasons, Peterson was being asked to name the best running back in the league.

It's a setup question when tossed out to someone of Peterson's abilities. Naturally, Peterson bristled at the notion that Johnson was better than him.

But Johnson kept piling up the yards before reaching the exclusive 2,000-yard club (2,006). Meanwhile, the same question kept being lobbed at Peterson and Johnson just to see what they'd say.

Johnson wasn't shy about declaring himself the best running back in the league. Meanwhile, Peterson's initial reaction usually was to answer the question with a question: "Who do you think is the best?" Then he'd smile and keep the conversation professional, but assert his competitive side.

In 2011, Johnson was a training camp holdout. It took the Titans coughing up $54 million over four years to get him back to work. Peterson congratulated him. Weeks later, Peterson topped him with a seven-year deal worth up to $100 million.

In 2012, Peterson joined Johnson in the 2,000-yard club, rushing for 2,097 in the season that immediately followed a knee reconstruction.

Now, two seasons later, Johnson has been released by the Titans as the age of the devalued running back position marches on. Tennessee chose a $4 million salary cap hit and no Johnson over a $10 million cap hit and Johnson. And while Johnson didn't have the greatest season a year ago, he's still a durable and productive back under the age of 30 (29 on Sept. 23).

Johnson has missed only one game in his career and is one of only six running backs to rush for at least 1,000 yards in each of his first six season. Four of them are in the Hall of Fame.

But a career-low 3.9-yard average per carry was lackluster enough for the Titans to dump him.

On a conference call last week, Peterson was asked about a trend that's seen a pass-oriented league devalue running backs. Former Vikings running back Toby Gerhart's $4.5 million in guaranteed money is the most by a 2014 free-agent running back and is less than kickers Robbie Gould ($8.85 million) and Dan Bailey ($7.5 million) and punter Pat McAfee ($5.3 million). Johnson is expected to land a relatively modest deal, and no running back is expected to be taken in the first round of the draft for a second straight year.

"You know, it's just kind of how it is, unfortunately," Peterson said. "There are a couple of guys who are different from that. I feel like I'm one of them."

Peterson then made it clear that his one-time rival wasn't one of them last season.

"Chris Johnson, maybe if he would have ran for 1,800 yards, he'd have a different story about how much he could be bringing in [this year]," Peterson said.

"It's all about what have you done for me lately. Unfortunately for the guys who were in free agency this year didn't have incredible numbers or incredible seasons to be able to get the type of [money] they wanted in free agency. I feel like that's it. I feel like me and a couple of other guys are going to keep it alive as far as running backs being able to come out and keep the running back position at a top level. That comes with guys putting in the hard work and being able to produce and show that when they step on the field."