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Myths and Realities of Aging and Wearing Running Backs

Over the past few seasons there have been a number of articles written about aging and wearing running backs. We used to hear that the age where a running back would decline was 31 but more recently we have also heard 30 and sometimes even 28. Many are also suggesting that Clinton Portis will struggle this season because he has reached 2,000 carries in his career. I decided to test out all these theories to find out once and for all, when do running backs really decline?

The first step was to look at the chances of running backs suffering injuries or not seeing the ball anymore as they get older. I decided to look at the number of running backs that had 200 touches in a given season and then see how many manage to have 200 touches in the following season as well:

As you can see, as running backs get older there is a smaller number that reach 200 touches. However, the interesting number is the percentage that can keep it up in the following year. It seems there are two interesting drops: the first one is when running backs turn 28 in the following season and the other one is when they turn 30. However, the percentage of running backs that continue to have 200 touches is higher for running backs turning 31 and 32 than for those turning 28 and 29. In other words, this would mean that running backs that manage to get past the age of 30 are not at risk until they turn 33; for me that does not make much sense. In my opinion that 37.7% is just a coincidence and you just need to be aware that running backs who are 28 years of age or older are more at risk.

This season we hear that LaDainian Tomlinson and Brian Westbrook are more injury-prone since they will be 30 when the season begins. These two players should be ranked lower than they were last year not because they are 30 but because one struggled with a toe injury early last year and had a groin tear later in the year while the other struggled with injuries all his career and just had ankle surgery. Both of those players slowed down in 2008 at the age of 29 and are risky selections because of that, not because they are now 30.

The next step is to look at whether or not running backs see a decline in performance as they get older. In this chart we will look at the average fantasy points for the running backs that had 200 touches or more in two consecutive seasons:

As you can see, until running backs turn 32 there seems to be no significant drop in performance. Running backs turning 30 actually perform better than at any other age if they get their 200 touches. This could be due to other factors and our sample is too small to come to any conclusions on that. Here is a chart where we grouped running backs who are 25 and 26 (turning 26 and 27) together and those 27 to 30 (turning 28-31) together:

As you can see, the difference between the two groups is only 1.6% or about four fantasy points which is nothing to worry about. This shows that the performance of running backs declines when they reach the age of 32 but not before that. This season there are no running backs that fall in that category.