It's been a rough offseason financially for running backs. And it's about to get worse with the Titans reportedly getting closer to releasing Chris Johnson.

Johnson is 28 years old. He's been in the league seven years. The only time he didn't have a 1,000-yard season was the year he had a 2,006-yard season. His career average per carry is 4.6 and the only NFL game he's ever missed came in 2008, his rookie season.

So he's young, durable and productive. But this is the 21st century and star running backs for the most part are becoming obsolete, if they haven't already reached that point.

According to NFL.com, six of the running backs listed among its top 101 free agents this year are going to be paid an average salary ($2.89 million) that's less than the average salary ($2.91 million) of the league's six highest-paid punters.

As for the future of the position, well, last year was the first time since 1964 that a running back wasn't taken in the first round. This year's draft could make it two in a row without a back taken on Day 1.

Johnson will make his next team very happy. But that next team won't make him as happy financially as he would have been had the Titans chose to continue paying him according to that four-year, $53.5 million deal he signed to end a 35-day holdout in the summer of 2011.

Remember that deal? As good as CJ2K was, eyebrows were raised because it came with $31 million in guaranteed money.

A few weeks later, in San Diego on the eve of the Vikings' regular-season opener, Adrian Peterson topped it when he signed a seven-year deal worth up to $100 million with $36 million guaranteed. He got $40 million of that money in his first three seasons, which just concluded.

Johnson will be released because he was due to make $13.5 million this season. The cap number is $10 million. Releasing him saves $6 million in cap space.

With Johnson's contract about to be thrown out the door with him, Peterson is the only running back in the league with a cap figure over $10 million. He's at $14.4 million. The next highest among running backs is LeSean McCoy at $9.7.

Obviously, Peterson isn't going anywhere this year. But the chances of him making it to the end of 2017 as a Viking under the terms of his seven-year deal are small, if non-existent.

The 2016 season is the first year of the new stadium and the first year that there is no dead money in Peterson's contract. His cap number is $15 million that season and $17 million the following season. So if the Vikings wanted to, they could cut him in either of those seasons and save that full amount against the cap.

Peterson will be 31 in 2016.

Of course, a lot can and will happen between now and when the Vikings will be forced to take a hard look at whether Peterson's cap number makes sense. And that's not to say the Vikings and Peterson wouldn't renegotiate more cap-friendly terms to keep him in purple for his entire career.

But in light of what's going on with running backs in general and Johnson in particular, it does make you realize that reality can be harsh even for productive members of the 2,000-yard club.