The Backup Effect: How Backup RBs Transition to Becoming a Starter (Fantasy Football)

Introduction

Every year we find ourselves watching a backup RB tear up the field every time they get a touch and think: if they only had the opportunity of a starting RB, they’d be so dominant! Sometimes these thoughts become reality, and these backups do get a chance — the problem is, they don’t always pan out. In this article, we’ll explore how backup RBs transition to becoming starters. Let’s get started.

Analysis

First, to set up this analysis, I gathered rushing data from 2017-2022, and ranked each team’s rushers 1, 2, or 3, based on the number of touches they saw in the given season. With this, we can now compare stats between starters, backups, and third-string backs. We hope to see whether or not there is a “backup effect” where backups perform better on limited opportunities because defenses aren’t expecting them to get the ball.

First, let’s look at rush yards per carry. When we plot the distributions for average yards per carry, all three levels fall to similar means. The starters naturally are more consistent, with the backups having a bit more variance. This doesn’t tell us much off the bat.

Next, we’ll look at fantasy points per carry. We see similar results, however, there are a couple of standout blips in the distribution of RB2s — it appears that sometimes, backup RBs outperform starters from an efficiency viewpoint — the backup effect in action.

While the margins are slim on average, there is clearly a category of backups that outperform their lead-backs on a per-touch basis in fantasy. These are the Tony Pollards and Alexander Mattisons of the fantasy world.

Next, we can look to see if there are any significant changes in these stats for RBs who started as a backup and became a starter. Looking at fantasy points per carry, there doesn’t seem to be much difference during this transition, however, there are a few outlier cases where backups put up incredible numbers which didn’t translate when they got more touches. Again, this is a case of the backup effect on the top echelon of the RB2 class.

We see similar results again looking at rush yards per carry — there is a minute difference in average performance for backups transitioning to becoming starters, but for outliers, it is difficult, if not impossible, to produce at the same rate.

Looking at some historical references will help illustrate this phenomenon. While it is clear that most RBs transitioning to a starting role continue to produce at a similar rate, it has become evident that highly efficient backups typically don’t continue their hot streak. Below, I selected a few notable backs from recent years who have become starting RBs — some who were incredibly intriguing as backups (Austin Ekeler, Tony Pollard, Alexander Mattison), and others who were unknown (Cordarrelle Patterson, Rashaad Penny, Khalil Herbert, Rachaad White). I plotted each of their fantasy points per touch for each year as a backup as well as their first year as a starter.

The results are very telling. The backs who had a lot of buzz as backups and produced high numbers as RB2 had a sharp dropoff during their first year as a starter. On the flip side, the players who put up relatively average numbers as backups continued this trend their first year as a starter, or even exceeded expectations, in the case of Patterson.

In the graphics below, the first year as a starter is highlighted in blue and in a diamond box

The same can be seen when we repeat this exercise with rush yards per carry.

Conclusion

The backup effect is real — sometimes. If a second-string running back is putting up very efficient numbers, it is unlikely that they will continue their pace as a starter. Approach these cases with caution! As for the rest of the backup RBs who earn starting roles, if they are putting up average, or close to average stats behind their lead back, they will likely continue to play at this level as a starter — and if you get lucky, they could even break out!

That’s all for this article, as always, feel free to reach out on Twitter with any questions!