Running Backs "Football Age"

In the NFL, running backs have the shortest careers. But how do we know when they are done? It seems like one season a running back peaks, and two years later their team releases them. This past off season is a great example of this. Warrick Dunn was released; the same goes for Fred Taylor and Deuce McAllister. McAllister and Taylor are both the career rushing leaders for their franchises, and Dunn is 3rd for Tampa Bay. Another big off season question we heard was what the Chargers were going to do with LaDainian Tomlinson. At the start of the season, Tomlinson will be 30, which seems to be the beginning of the end for running backs, plus they just used the franchise tag on Darren Sproles.

So, why don’t the teams show these players more respect? Other than the obvious “business side” of football, these players were in the twilight of their career. But do any of these running backs have anything left in their tank? It’s really hard to say that one thing determines when a running back is finished. Of the four running backs I mentioned above, all have different ages, seasons played and rushing attempts. I think that you have to use a combination of numbers to say how much a running back has left.

By using a running back’s age (as of September 1st, 2009), seasons played, games played, rushing attempts and total touches, I determined how much a running back has left in their “gas tank” and therefore, their “football age”. I used data from the top 200 retired running backs based on attempts taken from the great http://www.pro-football-reference.com/ , and fit a polynomial line to it. This is what I came up with.

With 65 being my retirement age, you can see that there are several player very close to being finished. But what does this actually mean? Brian Westbrook is 55.74 “football years” old with .21 left in his gas tank. Is Brian two years or three years away from retirement and in those years, how many yards and TDs can we realistically expect from him? Well, based on their gas tank, and the running back’s career numbers, I have determined how much production a running back will have left, if they continue to play.


So as you can tell, the projections are a lot better when the running back has played a handful of seasons. Also, I found that running backs that are in the Pro Football Hall of Fame average about 10 more “football years” old than the average running back when they retire.

It would be silly for me to say this is exactly how each running back is going to finish his career. I think of it more as an expectancy of a running backs stats.