The Fantasy Mythbusters: Are Insurance RBs Worth a Roster Spot?

For fantasy managers that invest high draft capital in a running back, a popular strategy can be to roster an ‘insurance RB’ as well. These are, simply put, the real-life NFL backups to stud football running backs, and thus are in line to receive a major workload if the starter goes down. This season, we’ve had some examples of notable insurance backs coming to the fore: Alexander Mattison saved Dalvin Cook fantasy managers with the sixth-best RB performance of Sunday, Chuba Hubbard will likely be the top waiver target this week with Christian McCaffrey sidelined, and Tony Pollard might even end up outproducing Ezekiel Elliott in Dallas.

Even though these insurance backs might not be as talented as the starter (otherwise they would be the starter) volume is king in fantasy. When thrust into a starting role, backups should be able to deliver solid performance for your fantasy roster. Plus, it means that you don’t have to worry about a calamitous injury to one of your stud RBs wrecking your entire fantasy season; you have the backup that will slide into the workhorse spot.

However, this is not a strategy without controversy. Roster spots are incredibly valuable in fantasy leagues, especially in-season. You might be clogging a spot on your bench for a running back that will never be valuable: injuries, ultimately, are relatively uncommon. Plus, there’s no guarantee that if the starter goes down the backup will actually perform well: you may recall the aforementioned Alexander Mattison posting a measly 26 rushing yards against the sieve-like Atlanta Falcons when Dalvin Cook sat out in Week 6 last year.

With this in mind, we can try to answer a simple question: is it worth it to roster an insurance back? Fantasy data comes from nflfastR, ADP data from the fantasy football calculator.

Methodology

We will consider running backs drafted in the first or second round since 2015; this is about the level of running back where you might consider investing in the backup. This year, it was Clyde Edwards-Helaire, and it’s possible as the CEH manager that you would want to slot Darrel Williams into the last spot on your bench.

Then, we can collect the highest-scoring running back – outside of the actual stud RB drafted early – on the same team that year. There are rare cases, as we will see, where the backup actually ends up outperforming the starter drafted early on the season (usually due to injury or a holdout). We can then analyze the performance of these backups throughout the season:

I’ve labeled the top three backup running backs here. Tarik Cohen had a great ‘gadget’ year behind starter Jordan Howard in 2018: he ran for 3 touchdowns, caught 4 more and even passed once for a score. The other two backs were beneficiaries of the same player – Le’Veon Bell – missing time: DeAngelo Williams had his career swan song in 2015 when Bell went down with an MCL injury and, of course, James Conner paid off in a massive way when Bell sat out for the entirety of the 2018 season. These were all basically league-winners (or season-savers): they delivered massively on a minimal investment (last pick in the draft or a waiver wire add).

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One aside: two of the top ‘insurance backs’ were Steelers backups that became the starter early on. In addition to player skill, this is likely due to head coach Mike Tomlin’s propensity to run the ball, and to run it mostly through a single player. This speaks volumes for Najee Harris‘ upside this year – who finally ‘broke out’ in Week 3 – as well as for any Steelers back that can take charge of the backfield.

Still, though, most of the lines appear to end up with relatively low scoring totals; there are also plenty of flat sections (where no games were played) and early cutoffs (where the end of the season was missed). Let’s quantify what some of these backups performances actually looked like

Backup Performance

Here’s a histogram of the actual points scored by backups when the starters don’t play. This makes sense in a fantasy context: you likely aren’t starting the backup when the stud starter is playing, so it makes more sense to think about backup performance when the starter is out (and you will start the backup). Here’s the chart, with the red line showing the median:

The median points when backups start is 10.9 points, with a mean of 13.3 (thanks to some right skew). If we take out James Conner and DeAngelo Williams, who are truly exceptional cases, the chart looks like this:

With these two players removed, the median is just below 10.0 points a game.

Anyways, an RB were to play the whole season with a median PPG of 10.9 points (so including Conner and Williams in the data), they would finish at about the RB15 or RB16 overall. The implication is that, when your backup gets the start, they are a solid RB2 in your lineup. This is intuitive: they might not be as good as the stud starter, but the workload they receive will still add value to your roster.

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Backup Usage

We’ve seen some examples of legendary backups, and have looked at the performance of backups when they do get to start. However, one major question remains: how often does having this insurance pay off? How often will the starter go down, and the backup be thrust into the limelight?

Here’s a chart that gives the starts made by a backup – in a full season – on the x-axis, and the number of these occurrences – since 2015 – on the y-axis:

This chart might be a bit surprising, especially since we tend to remember the outlier cases when a starter is injured or sits out. However, in the vast majority of cases, the backups actually won’t get that many starts. This is because starters almost always make it through most of the season, and because backups might not have a strong claim to the job and could easily lose their spot to someone else on the depth chart. Even DeAngelo Williams mentioned above as an exemplary backup case, only started nine games during the fantasy season.

Anyways, to put numbers on it, this chart tells us that backups make more than 1 start in a season just 41% of the time. They make more than two starts just 32% of the time, and make no starts 42% of the time! Basically, the majority of backups will see the field (as a starter) once or less, and the vast majority won’t see it more than twice. We can now turn to our conclusion:

Myth…

In most cases, BUSTED. Backups are ok when they get to start, putting up decent RB2 numbers on average. However – more importantly – they barely get to start. It is not at all common for a backup to start more than twice; it’s more likely that they never start at all. In addition, this analysis ‘guesses’ almost perfectly who the second fiddle RB is since we look post-hoc at whichever back actually scored the most (outside of the starter). In real-life situations, this might not be so clear: for muddled backfields, it can be difficult to project who will get most of the work if the starter goes down.

This isn’t completely busted because there is some level of nuance here. The question to roster an insurance back or not all comes down to comparable value: which player are you losing out on by clogging a roster spot with a backup? This depends on a lot of factors: size of the league, needs for your team, waiver wire activity, etc. that are difficult to address in a broad and general way in this article. However, I think it’s safe to say that, in most cases, your last bench spot would be better filled than with an insurance RB who is expected one or two (or zero) starts with RB2 production.

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Also, there is some real upside to rostering insurance backs. The stated examples of James Conner, DeAngelo Williams, and Tarik Cohen – as well as Mike Davis filling in for an injured CMC last year – all produced significant value for basically no draft capital. These players represent a long ‘right tail’: they end up starting many games and delivering a ton of production for your team. For that reason, it might be reasonable to shoot for the stars (or shore up your team) with a backup, especially if the starter is injury prone and the bell-cow backup situation is secured.

Finally, when it comes to Tony Pollard, Alexander Mattison, and Chuba Hubbard at this moment in time, don’t hear what I’m not saying. All three of these backs have the context that supersede some of the broad strokes of this analysis. For Mattison and Hubbard, the starting RB is either guaranteed to be sidelined for a few weeks or has a real chance of missing more games; this implies a heavier backup usage than usual for an insurance back. It’s like buying fire insurance on a burning house: the starters are already injured, so if you can get the insurance for a good price, you should! For Pollard, we’re not even sure if he is a true backup to Zeke, or playing a role similar to Kareem Hunt – the RB1 this past Sunday – in Cleveland. This analysis applies more to traditional backups with currently healthy starters: Tony Jones Jr. in New Orleans, Devontae Booker in New York and Jeremy McNichols in Tennessee are good examples.

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