There is extensive discussion on the internets (such that you needn't take my word for it) over the proper amount to utilize running backs so as to maximize their efficiency, health, longevity, and the like. The Rule of 370 is one such theory and can be read about it more detail here. Like most things, a more nuanced discussion would be better than merely posting the now almost mythical number of 370, but the theory is something like: Running backs who carry the ball 370 times a year generally decline in production the following year.
We can haggle and argue over whether the rule is true or the number is right or the extent to which other factors should be included (like receptions) or other appropriate alterations to the slowly emerging conventional wisdom. But enough of this is intuitive where I'd rather we not have that extended talk, which could take pages. Briefly: There is hardly anything controversial about suggesting that the running back who runs more often will suffer in production and health. Nobody can run forever. And being tackled is the result of the vast majority of runs, and tackles cause both short-term (injuries) and long-term (wear-and-tear) damage to the fragile human bodies we are all confined to. If 370 is just a number, it is at least a figure that communicates the undeniable truth that the better you manage a running back, the longer you'll have him.
Homer McFanboy, in a great post on the statistical development of Jason Campbell, Santana Moss, and Clinton Portis, touches on the running back use concept cited above only tangentially. I've added emphasis:
Portis is on pace to finish the 2008 season with 344 carries for 1,476 yards and 12 touchdowns. As a refresher, Portis finished 2007 with 325 carries for 1,262 and 11 touchdowns. Last season Portis was picking up 3.9 yards per carry, while this season he’s averaging 4.3 yards per rush. While some folks quietly grumble that Portis is coming off the field too often during games, the numbers show he’s still being very productive. Any way you look at it, the Redskins are in good hands with Portis.
I imagine by "some folks" one could just as easily substitute Brian Mitchell, and by "quietly grumble" you could sub in "shout regularly to anyone and everyone who will listen." But I also imagine that many Redskins fans do feel the same way, that our highly paid starting RB is there to run the football, and he can't do that from the sideline. I'm sure that position deserves a better advocate than yours truly, but I'd sum up it as:
1. You pay the player a lot of money to play, therefore said player should play.
2. You want your best players on the field.
And reader(s) can add in any number of similar justifications, of which there are legion. However, I disagree with it, and actually feel more comfortable with the general proposition that Clinton Portis run less.
Portis is highly paid. Although he is something like the fifth highest paid player per year on the team, his contract is the largest, at 53M, largely because he has huge escalating salaries come 2010 through 2013. Let that sink in: Clinton Portis is under contract through 2013.
In so far as the first argument above is a financial appeal, I say the only reasonable financial strategy is the one that maximizes return over the course of the entire contract. While we want to get the maximum production out of Portis now, if that necessitates much less production later in his career, for potentially much greater cost as his salary escalates, are we really making the sane financial choice? I doubt anyone in Jacksonville is lamenting the fact they didn't use Fred Taylor more in 2002 (one of like two years he was healthy), especially while he was accumulating a career high 5.4 yards per carry on 223 rushes just last year. And he ain't done yet, which means the Jags could get a huge amount of value out of a 31 year old running back. Four years from now I'd love to be talking about that great 100 yard rushing game Clinton Portis had. But if we rush him 400 times a year the odds of that happening are slim but approaching none.
Consider: Portis approached the scary 370 number in 2004 (383 touches counting receptions) and again in 2005 (382 touches counting receptions). The following season he was injured for much of the year and, as a result, suffered a substantial decrease in production. He had 372 touches last year, an only slight decrease that was actually lower than many of us imagined given how well Betts played. Right now Portis is on pace for 368 touches, and I'm fine with that. I'd be fine if we lowered it, actually, for reasons I state below.
To the second argument, I'd add that while true, the Redskins are unique in that we have an excellent backup running back who represents only a potential marginal decrease in production. Not a lot of teams have the luxury of two good RBs, but we do; Ladell Betts rules. Behind the same offensive line, in the same system, the two have remarkably comparable statistics: Since 2004 Portis is averaging 4.04 YPC. Betts, under the same time frame, is rushing for 4.22 yards per carry. While each runner has his own unique style and strengths, I think most agree Portis is better. But if he is indeed better, it ain't by nearly as much as most Redskins fans probably think.
The bottom line is, and maybe I'm stupid, the current policy of Portis policing himself and pulling himself when he feels he needs a breather is just fine by me. While I acknowledge the necessity of putting your best guy on the field, that theory applies equally towards the future, and thus maximizing the amount of production Portis has in 2009 is comparably important to maximizing his production now. We have a quality backup who, when placed in the game, produces comparable yards per carry. We will get more out of both of them if we can prolong their careers by mitigating the amount of damage we do the players by overuse. As much as I grew to hate Running Back By Committee systems as a Fantasy owner, it is very much the norm in the league and would serve the team's long term interests better, in my opinion, than putting more emphasis on Portis touching the ball 400 times a year. I'd be cool at 350.
Because I'd be cool regardless. But you guys already knew that (how cool I am, I mean).