Maurice Jones-Drew's Retirement Underscores Mortality of NFL RB

There's a saying that, in addition to standing for National Football League, the letters "NFL" also stand for "Not For Long."

No players in the NFL know this better than running backs. The trip from the penthouse to the outhouse in the backfield can happen in the blink of an eye.

With free agency set to kick off March 10 and a large group of aging running backs looking for work, we received another sobering reminder on Thursday that Father Time is undefeated.

Thursday afternoon, Oakland Raiders running back Maurice Jones-Drew announced via his Twitter account that he's calling it a career after nine years in the league:

The 29-year-old Jones-Drew, who played most of his career with the Jacksonville Jaguars, joined the Raiders in free agency last year. Now, after one disastrous season with the Raiders that saw Jones-Drew put up career lows across the board, he's not only out of Oakland but out of the NFL altogether.

It's an unceremonious end to a fine NFL career.

Year	Team	G	Att.	Yds.	Avg.	TD	Rec.	Yds.	TD
2006	JAX	16	166	941	5.7	13	46	436	2
2007	JAX	15	167	768	4.6	9	40	407	0
2008	JAX	16	197	824	4.2	12	62	565	2
2009	JAX	16	312	1391	4.5	15	53	374	1
2010	JAX	14	299	1324	4.4	5	34	317	1
2011	JAX	16	343	1606	4.7	8	43	374	2
2012	JAX	6	86	414	4.8	1	14	86	1
2013	JAX	15	234	803	3.4	5	43	314	0
2014	OAK	12	43	96	2.2	0	11	71	0

For three straight seasons from 2009 to 2011, Jones-Drew topped 1,300 yards on the ground for the Jaguars. He averaged at least 4.4 yards a pop in each of those seasons and capped the run with a league-leading 1,606 rushing yards in 2011.

However, the 2012 season began with a contract holdout and ended with Jones-Drew on injured reserve with a Lisfranc sprain.

He was never the same after. In fact, since Jones-Drew led the NFL in rushing in 2011, he's gained only 1,313 yards over three seasons—including less than 100 in Oakland last year.

And his is a story that isn't finished playing out in the NFL this year.

Player	2014 Team	Age	2014 Yards
Steven Jackson	ATL	31	707
Reggie Bush	DET	30	297
Chris Johnson	NYJ	29	663
Frank Gore	SF	31	1,106
Justin Forsett	BAL	29	1,266
DeAngelo Williams	CAR	31	219

Jones-Drew may have decided to hang up his cleats, but there are other aging former superstars still hanging on across the NFL.

After gaining over 1,000 yards on the ground for eight straight seasons with the St. Louis Rams, Steven Jackson failed to hit that mark in either of his two seasons with the Atlanta Falcons. Now, after averaging 3.7 yards per carry for the Falcons in 2014, the 31-year-old is looking for a new home.

Ditto for Chris Johnson. Long gone are the days of "CJ4.24" and Johnson's six straight 1,000-yard seasons (including a 2,006-yard 2009 campaign) with the Tennessee Titans. They were replaced by 663 yards for the Jets in 2014, and after one season in New York, Johnson was shown the door.

Reggie Bush topped 1,500 total yards during his first season in Detroit in 2013, but the 30-year-old set a career low with only 297 yards on the ground in 2014. The Lions said no thanks and released Bush in February.

It's a fact that's equally inescapable and rotten. Due in no small part to the pounding they take advancing the football, running backs break down much more quickly than players at other positions. More than one study (including this one from Chase Stuart of Football Perspective from 2012) demonstrates that running backs begin to decline by the time they're about 28 years old:

"

This group of running backs (1990-2012) peaked at age 26, and had a four-year prime from ages 24 to 27. …Several running backs weren’t even active in the league by the time they were 30. Among all running backs, there was a very steady decline from age 26 to age 31 and then a sharper decline at age 32.

"

Yes, there are exceptions (Frank Gore topped 1,100 yards for the San Francisco 49ers last year at 31), but the overwhelming majority of running backs pushing 30 are either precariously close to the edge of a cliff or have already gone over it.

It's part of the reason why even young running backs have become devalued in today's NFL. It's an even larger part of the reason why these aging tailbacks are heading into a market for their services that's going to be frosty.

And it may well be why Maurice Jones-Drew came in from the cold and called it a career.

Gary Davenport is an NFL Analyst at Bleacher Report and a member of the Fantasy Sports Writers Association and the Pro Football Writers of America. You can follow Gary on Twitter at @IDPManor.