Of all the players on NFL fields in the fall, running backs are the most fragile breed. I know this, you know this, they know this, general managers know this, and owners know this.

That common knowledge leads to an impasse, and the 2012 approach to the position in which running backs are regularly treated like your favorite pair of awesome, super comfy socks. They’re the ones you wear daily around the house during times when you’re wearing little else, and then suddenly–no, abruptly–they develop holes and deep wounds, and their end is near.

They are the NFL’s mules, and nearly every offseason there’s at least one running back who sees that father time is closing in, and knows he’s in a position to get paid one more time. Usually, said running back isn’t satisfied with his team’s response to his demands, and then a battle of leverage begins.

Welcome to Maurice Jones-Drew’s existence for the next few months.

The mighty, pinball-like human who led the league in rushing last year with 1,606 yards and was the only RB to average more than 100 yards per game thinks he’s outplayed his current contract, and he wants a restructured deal. He has two years left in the five-year deal worth $30.95 million with $17.5 million guaranteed that he signed in 2009. He’s due to make $4.45 million in 2012, and $4.95 million in 2013, a two-year total that falls behind other top 10 running backs. For example, Marshawn Lynch finished seventh with 1,204 yards (402 yards less than MJD), and he’ll make $12 million over the next two years to Jones-Drew’s $9.4 million.

So based on his sheer numbers and how much he blew away his peers (Ray Rice finished second in rushing, and he was still 242 yards behind Jones-Drew), he’s earned a raise, and can completely justify a hold out.

But based on his age, he can’t. Jones-Drew is 27, which is young in human years, but not running back years, which accelerate the aging process slightly more than dog years. He likely only has two-to-three years of elite production left, and maybe less after three straight 300-carry seasons (he had 299 in 2010, if you’re the bickering type).

That’s where the rigid battle line has been drawn, and that’s why Jaguars general Gene Smith is sitting tightly in his bunker, not moving an inch. Here’s his quite polite way of telling Jones-Drew to piss off

“He has expressed that he would like to renegotiate and we have expressed, again, that we feel he has a contract with two years left and we expect him to fulfill those obligations”

Jones-Drew is being held back by the usual set of circumstances in his pursuit of one last lucrative deal. Again, most notably his age, but also recent running back contracts around the league that have quickly become gargantuan anchors.

Chris Johnson missed all of training camp last August in his own powerplay for a new contract, and it resulted in a six-year deal worth $55.6 million, $30 million of which is guaranteed. He was 25 at the time and two years younger than Jones-Drew, and he rewarded the Titans by having his worst season, and rushing for only 1,047 yards. Tennessee seriously considered cutting Johnson less than a year after that massive deal was signed.

Then there’s DeAngelo Williams, another high earner and under-performer who was moronically re-signed by the Panthers to a five-year deal worth $43 million and $21 million guaranteed last summer despite his age (28). He had only one 100-yard game in 2011, averaging 52.2 yards per game.

The stalemate could officially begin tomorrow if Jones-Drew refuses to report to Jacksonville’s mandatory mini camp, in which case the Jaguars can fine him up to $60,000 per day. If that happens and the yearly high-profile running back quagmire begins, picking a side is difficult, but seeing who has far less leverage is easy.

The aging running back will always lose. Always.

A player who’s outplayed his contract despite being the focal point of an inferior offense needs and deserves a raise during his final years of elite production. But his team is hesitant, and understandably leery of committing to an investment at a position that historically has poor durability.

There will be a compromise eventually, but it may take the loss of training camp time during what will ultimately be a failed effort by Jones-Drew.