Another reason for the lack of investment in running backs is the flat distribution of talent at the position. The crop of NFL running backs is impressive; every year late-round or undrafted running backs on rookie deals break out and put up impressive seasons. Examples from recent seasons include (but are not limited to) Aaron Jones, Phillip Lindsay, Raheem Mostert and Austin Ekeler. The combination of the lack of importance of a strong run game and the distribution of talent in the backfield has led to some teams adopting the approach of running back by committee. As the name suggests, instead of concentrating the vast majority of running back into one player, some teams are spreading carries out between two or three players. The benefit of such a strategy is twofold: running back committees are cheap because there is not one dominant player who commands a large salary and it is flexible in case of injury which, given how often backs tend to get hurt or breakdown, is an important consideration. With the running back by committee becoming a more pervasive strategy the past several seasons, I thought it would be worth investigating which teams were most and least committed to the approach in 2019 and how those teams have fared on the ground and on offense overall.
I first looked at the top half of the league in terms of percentage of running back carries allocated to the RB1, nominally the starter.
Carolina, Cleveland, Cincinnati, Tennessee, the Giants, and Dallas all make sense at the top of this leaderboard given both the reputations of their starting tail backs and their investments in those players. The Jaguars stuck out last year because they gave a higher proportion of their carries to their RB1 than the teams employing well-renowned ball-carriers Nick Chubb, Derrick Henry, and Ezekiel Elliott when their RB1 was Leonard Fournette. Recall my analysis of Saquon Barkley (and its addendum). If you look at the visuals for the high-volume running backs, Fournette fairs poorly compared to his peers as both a pass-catcher and ball-carrier. Maybe it was on account of a lack of options (though we know the distribution of running back talent is flat) or sunk cost fallacy (they invested in him with the fourth overall pick). Nevertheless, giving a back of his demonstrated ability that much volume was actively hurting the offense. Others of note include Washington, Houston, and Chicago who employed Adrian Peterson, Carlos Hyde, and David Montgomery as their RB1s, respectively. Their heavy usage can be attributed to the fact that the backups for these teams were satellite backs Chris Thompson, Duke Johnson, and Tarik Cohen. Aaron Jones for Green Bay also saw a lot of work. Under Mike McCarthy, the team had one of the more flat splits in carries year over year, but under Matt Lafleur Jones saw a lot of work. I am very interested in how often Green Bay uses second-round rookie A.J. Dillon after neglecting to choose a wide receiver in one of the deepest drafts in recent memory. Now, let's look at the RB1 laggards:
The team that sticks out is the team and coaching staff that provided the impetus for the study: the San Francisco 49ers under Kyle Shanahan. Unlike his father, whose zone running scheme made superstars out of unheralded prospects like hall-of-famer Terrell Davis, Clinton Portis and Mike Anderson, Shanahan has favored by committee type approaches to his running back depth chart. As one can see, the RB1 and RB2 had the same share of carries (137 each for Coleman and Mostert), with the RB3 lagging by about three percent (Breida at 123). This degree of uniformity was unmatched across the league. Pittsburgh's flat distribution was a consequence of an injury to James Connor. Arizona looks to have a committee, but after trading for Kenyan Drake he saw the majority of the work out of that backfield. Philadelphia was similar to Arizona, but for the Eagles there was not a trade; instead rookie Miles Sanders took the reins in the back half of the schedule. Baltimore, the most effective ground game by EPA per play, used a committee approach with Mark Ingram, Gus Edwards, and Justice Hill. I would expect something similar this year, except with second-round draft pick J.K. Dobbins either as the RB2 or RB1 if he flashes more than Ingram. Gus Edwards is the epitome not wanting to invest too much into running backs. After being undrafted out of Rutgers, he has averaged 5.3 yards per carry across two seasons.
Finally, I wanted to see if there was any signal in running back utilization affecting running efficiency, play calling tendencies, and overall offensive efficiency.
RB1 usage had almost no affect on running play success rate (percentage of plays yielding positive EPA) or EPA per run by running backs (I filtered out quarterback carries). The correlations for the two were 0.0132 and 0.0059, respectively.
Oddly enough, teams that used their main running back the most threw the ball slightly more (R-squared of 0.0175, so mostly noise). I think this very small correlation is the product of the teams who used their RB1 the most were not very good (for example Carolina, Jacksonville, and the Giants), thus had many negative game scripts.
Of all the statistics I looked at, the relationship between RB1 work and overall offensive efficiency had the strongest relationship (strongest being relative, still an R-squared of 0.0605). My hunch is that teams tend to shy away from committees when they invest heavily in their RB1. By investing heavily in your RB1, inherently you neglect investing in other offensive positions that have a greater effect on offensive success. The reason reason the relationship is not especially strong is that not spending on your RB1 also allows you to spend more on defense (so not all of the savings go to offense).
Overall, the main takeaway is that using a committee approach (and not spending precious capital on a star running back) has basically no affect on both rushing efficiency from running backs or overall offensive efficiency. Thus, all else being equal, it would be wise to find two or three backs at little cost and concentrating resources on the passing game. Carry distribution is a function of coaching philosophy, resource allocation, and perceived talent on your running back depth chart. I will be keeping an eye on how some of the new head coaches use their running backs, especially McCarthy in Dallas who has never had a running back with the reputation of Elliott. San Francisco is another team to watch. After utilizing an egalitarian split during the regular season, Mostert was one of the most-talked about players in the playoffs and had a public trade demand before his contract was restructured. Will Shanahan continue to boast the same type of committee? We will soon find out with the season starting in just a few days.
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