Home > FNQB, NFL > FNQB: Does splitting carries improve running back performance?

FNQB: Does splitting carries improve running back performance?

Editor’s Note: This week, Brian is taking over the Friday Night slot at LiveBall Sports with a piece featuring proprietary research on the relationship between splitting carries and rushing efficiency — Greg

One nugget of conventional wisdom in football is that splitting carries between running backs will improve the overall running game by resting players, exploiting defensive weaknesses and keeping the opposing team off-guard. At least anecdotally, this season has seen fewer prominent featured backs and much more situations where players are splitting carries. The basic analysis in this article will not debunk or support that idea — nor should we seek such an absolute rule as teams differ in their philosophy and personnel and the landscape of the game is constantly changing.

To try to answer the question posed in the title, I compared the percentage of running back carries that went to the primary running back with the primary back’s DVOA so far through the 4 weeks of the season. This is an inherently flawed approach as injuries, opponents, lack of defensive adjustments and random variance have all added a lot of noise to the data. Nevertheless, any conclusions or hypotheses made can be looked at over a larger time frame and tested yet again to try to gain some understanding.

Results
Below is a chart where the featured back’s DVOA is plotted against the percentage of carries that back has received of his team’s total running back carries.

As expected, there is no clear trend line in one direction or there other. However, we can see four out of ten running backs who carry the ball above 75% of the time have a significantly negative DVOA below -10%. Of the ten backs that have received over 75% of their team’s running back carries, only 4 have been showed a positive DVOA. Of the other 22 teams who split carries more evenly, only two have a DVOA below -10% with eight performing at below average levels. Clearly, there is nothing that says a back who is featured prominently is bound to fail, but there is a slight trend. To gain a little more insight, we can look more closely at three groups I will call High Performers, Workhorses, and Duds.

High Performers
For the sake of this analysis, we’ll call the high performers any featured back with a higher than 20% DVOA on the year. The four who fit the criteria this year are Arian Foster, LaDainian Tomlinson, BenJarvus Green-Ellis and Mike Tolbert. Not exactly the list anyone would expect before the season started, eh? Here are their respective share of the carries and DVOA:

Foster Tomlinson Green-Ellis Tolbert
% of Carries 73% 55% 47% 47%
DVOA 29.7% 25.6% 34.8% 34%

It is interesting that, of the four, three were relatively unknowns going into this year and one was anything but unknown. Since we are so early into the season, there are a couple of explanations aside from the low workloads. One, these players “snuck up” on defenses who have not yet adjusted or prepared properly for these running backs. Two, since we are so early into the season, there is a high chance of statistical noise, especially considering the less-featured backs have relatively few carries. In either explanation, a look back into this relationship later in the season will be highly beneficial.

The Workhorses
We’ll call the workhorses any backs with over 80% of their team’s running back carries. So far this year, there have been seven such running backs: Adrian Peterson, Darren McFadden, Rashard Mendenhall, Chris Johnson, Maurice Jones-Drew, Frank Gore and Cedric Benson. This list is a bit more familiar names, but the performance thus far has been lacking:

Peterson McFadden Mendenhall Johnson Jones-Drew Gore Benson
% of Carries 86% 83% 82% 86% 81% 94% 82%
DVOA 12.4% 7.1% 14.4% -21.2% -7.4% -3.9% -18.1%

The big surprise in this group is the twitter apologizing Chris Johnson who is coming off a huge workload of 354 carries and 50 receptions. Despite his 2,000 yards in 2009, he has been quite awful in terms of DVOA this year. While Cedric Benson had a lesser workload while still eclipsing 300 carries, he also was not the same rusher that Johnson was last year. It would be easy to conclude that splitting carries can improve performance on a multi-year basis due to player rest as there is also much work done on the impact of workload on a player. However, we may also see a bit of a trend that may correct itself over the course of this season as coaches feel pressure to give their prior season’s high performers a significant chunk of playing time. Once again, a look-in later in the season can give us a better look at the impact of a lot of carries.

The Duds
Finally, we get to look at the awful peformers thus far in the 2010 season who have posted a DVOA below -20% while receiving the most carries on their team. This year, those players have been Chris Johnson, who we have already looked at, Brandon Jackson, Carnell Williams and Matt Forte.

Johnson Jackson Williams Forte
% of Carries 86% 56% 76% 72%
DVOA -21.2% -35.5% -31.7% -44.8%

Here, we have a wide range of situations and level of carries. Johnson is the sole workhorse while Jackson is the only back sharing nearly 50% of carries. The best explanation for Forte and Jackson’s numbers is that they are simply not good rushers or are in terrible running environments. Last year they each respectively posted a -15.5% and -15.8% DVOA indicating that no amount of time splitting will make them into good performers. Carnell Williams was not so bad last year and significantly split carries, but we could be seeing his decline, some statistical variance or just a bad few weeks. The word is that he will start splitting carries this week, which will allow us to yet again look in later in the season and gain some insight.

Conclusions
On the surface, there appears to be evidence of a negative impact of a large workload on performance for running backs. Any evidence of splitting carries disrupting the ‘flow’ and hurting performance is not apparent at this time. Some backs, such as Adrian Peterson, have been resilient enough to continue a high level of play despite receiving a great deal of the carries for their team. A deeper look into this relationship later in the season as well as an analysis of the 2009 season will explore some of the issues and ideas raised in this article.

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