How Important Is the NFL Combine for Running Backs?

Two really important things are happening this week: the NFL combine is starting, and we get to find out who makes the final three on The Bachelor.

I'll just stick to sports here, though. (But you can find my Bachelor takes on Twitter.)

While some roll their eyes at the NFL combine's importance, I'll make the safe assumption that you're here at numberFire because you like numbers. And anytime you can get more numbers to help diagnose a situation in sports, it's a good thing.

The NFL combine is a good thing.

Now, we live in a fantasy football-driven world, which means a lot of football consumers are into quarterbacks, wide receivers, running backs, and tight ends. So, today, we'll look at the running back position and see how important this whole NFL combine process actually is for backs.

Does, say, a 40-yard dash time actually matter when compared to on-field NFL production?

Defining Success

The only way we can do something like this is if we set somewhat arbitrary parameters around success. That is, we're trying to figure out what successful running backs did at the combine, and the only way to do that is through some subjective, arbitrary process.

Fortunately, just a week and a half ago, I found a particular way to define success through the metrics we use here at numberFire.

What makes a running back successful? His ability simply to gain yards on the ground? His receiving skills? His pass-blocking?

Rather than diving into that rabbit hole, it's easiest to keep things simple: a successful running back is one who's good enough to see a lot of touches in his offense all while successfully improving his team's chances of scoring.

That seems fair, right?

Because most running backs won't sniff 300 carries in a single season (unless they're good), anything above that mark means they've more than likely had more than one year of seeing opportunity in an NFL offense. That'll define the touches part of all of this: any running back with 300 or more touches during his NFL career.

(This is very scientific.)

To determine if the back has helped or hurt his team through the years, we can turn to Net Expected Points (or NEP, which you can read more about NEP in our glossary), which tells us how many real points a player adds or loses for his team.

More specifically, our Success Rate metric shows us how often a running back makes a successful, positive expected-point play for his team -- it's the percentage of carries made by a running back that positively impacts his team's scoring chances.

Through the years, the average Success Rate for a running back has hovered the 40% mark. In other words, 40% of rushes have been deemed a success through our expected points model.

So we'll stick with that number as our production parameter: any running back with a career Success Rate of 40% or greater.

Combining those two aspects -- 300 attempts and a 40%-plus Success Rate -- gives us 51 different FBS (FCS isn't included, which admittedly lowers the sample a tad) running backs since 2005. That's the sample we're working with.

Given not every running back participated in the combine, that list of 51 shrinks to 44 for purposes of this study. But that's still not a bad sample to work with.

How did these guys fare at the combine?

Combine Results

Here's a look at the combine category averages within the 44-back sample versus the averages among all running backs (fullbacks excluded) who've participated in the event since 2005. (For those who are unaware, Speed Score is a way of adjusting a player's 40-yard dash time for his weight. Agility Score is a combination of a player's 20-yard shuttle time with his 3-cone time.)

There's definitely some noise here -- a lot of players have 40-yard dash times but didn't participate in any other events, for example. With that being said, we're looking at a 44 running back sample within a group of 349 total running backs, so it's not like one or two data points is going to shift the set considerably.

As you can see, things look almost identical throughout both groupings. That means there's not a whole lot that separates successful NFL running backs (or, at least, how we're defining successful ones here) at the combine from unsuccessful ones. Aside from -- maybe -- the 40-yard dash.

Like I said above, Speed Score takes the 40 time of a player and adjusts it for how much the player weighs. Because, naturally, the heftier the body, the slower it'll move. Isaac Newton said something about that once, I think.

The graph above shows the entire group of running backs who participated in the combine since 2005, charting their weight versus their 40-yard dash time. The trendline let's us know that, yes, the heavier the player, the slower he runs.

Anything above the trendline would be considered bad, and anything below it is good. Let's now overlay our successful running back sample onto this chart:

The over- and under-the-trendline split within the successful sample is pretty even, but the thing to note is how many of the slower-than-they-should-be players aren't that much slower than they should be. In other words, it's been very rare for a Speed Score outlier -- an outlier in the wrong direction -- to become successful at the NFL level.

In fact, of the 44 successful backs, only one had a Speed Score below 90, and that was from arguably the worst back in the subset in Jacquizz Rodgers. He honestly wouldn't have even been part of the sample had he not done what he did in 2016.

Meanwhile, 28 of the running backs had a Speed Score of 100 or better, giving them above-average marks.

This Week's Combine

Generally speaking, the combine's results don't really seem to matter a ton for the running back position, maybe aside from the player's 40-yard dash time. That's what you should be watching this week.

But that doesn't mean we shouldn't pay attention to outliers, and it certainly doesn't mean that all pre-professional numbers are irrelevant. As I showed last week, college production at the running back position can be a great way to determine NFL success.

Of course, the NFL combine isn't just for the measurables, either. It's for teams to get to know these players. It's for players to tell their story.

So while a strong showing may not be a big deal for these backs, we should never say the event itself is a worthless cause.