The 2012 season was "The Year of the Rushing Quarterback", where we saw a new breed of signal-callers who could not only deliver long-range strikes with their arms, but also strike terror into the hearts of run defenses with their legs. At the time, San Francisco 49ers new starting quarterback, Colin Kaepernick, was the pinnacle of this kind of threat to a defense, and fans and defensive coordinators alike had no idea what to make of it.

Actually, 20 years earlier, having inherited the 49ers’ starting job himself, Steve Young proceeded to shock opposing defenses not only with his cannon arm, but with his fleet feet as well. And nearly 30 years before that, Vikings’ quarterback Fran Tarkenton did the same. The running quarterback has been around since the modern era of the NFL, and technically even before, when the forward pass was illegal.

Seemingly since Tarkenton’s days, we’ve also heard the narrative that these dual-threat quarterbacks open up the run game for their backfield companions, the running backs. This idea states that, since defenses have to plan for the possibility of the quarterback throwing, handing off, or taking off himself with the ball, there's a greater confusion that a rusher can take advantage of. We saw Ricky Watters, the Niners’ lead rusher with Young, succeed greatly with a dual-threat quarterback. Yet, there wasn’t much to be said about the running backs in Minnesota with Tarkenton.

Is this a real effect? Can rushing quarterbacks warp the defense’s vision and allow their running backs to be more effective?

Clogging the Lanes

As a basis for this study’s exploration, we'll look at numberFire’s signature Net Expected Points (NEP) metric. NEP is, at its most basic core, a measure of how much a player increased his team’s scoring potential on any given play. In this study, we're focusing on Rushing NEP, which is the accumulation of expected points solely on rushing plays. You can read more about NEP and its various forms in our glossary.

To form the first part of this study, I took the last five years of quarterback data, pulling every team’s primary quarterback since 2009 (300 passing attempts or greater; if there were multiple quarterbacks, they became a team composite) and comparing their rushing metrics to their top running back's metrics. The specific statistics I evaluated were total rushing attempts, Rushing NEP, Rush NEP per attempt, Successes (the number of rushing plays a player made that gained positive NEP) and Success Rate (the percentage of total rushing attempts that were successes). The goal was to see how well quarterback rushes, Rushing NEP, Rushing NEP per rush, and so on correlated with running back rushes, Rushing NEP, Rushing NEP per rush, etc. Here are the results:

When evaluating correlations, a good rule of thumb is that anything above 0.40 (positive or negative) is a fairly strong relationship between variables, 0.20-0.39 is weak to moderate, and anything below 0.20 is a negligible relationship. As you can see, there's no correlation that is at all meaningful between any of these variables, though it does seem significant that the strongest such correlation is between the total Rushing NEP of quarterbacks and running backs. This may indicate that, the more valuable of a rusher the quarterback is, the more valuable the running back’s rushing becomes as well.

I also got a little creative with the correlations to see if there was anything that leaped out of the data. Turns out, there were a few correlations that were not only significant, but much stronger than that between quarterback and running back Rushing NEP.

While they still classify in the “weak to moderate” category, the correlation between quarterback Rush Attempts and both running back Rushing NEP and Rushing NEP per attempt are our strongest matches. What this seems to indicate in a larger sense is that the more a quarterback rushes, the more a defense expects him to rush, which allows a running back a greater opportunity to catch them looking the wrong way. If this is true, then it means that a rushing quarterback needs to work in volume in order to offer more value to his backfield.

Breaking One Off

In order to test this new theory, I concocted a second part to the study. Instead of looking at all quarterbacks, I took only the quarterbacks who were the most efficient rushers (a Rushing NEP per attempt over 0.20), and examined these same correlations with them and their lead backs. What I found was even more than I expected.

Most importantly, the strongest correlations we now see in this elite tier of mobile quarterbacks are moderate ones (a step up) between – as with the full pool before – quarterback Rush Attempts and both running back Rushing NEP and Rushing NEP per attempt. It appears that with the most efficient of NFL quarterbacks, this correlation between volume of rushing attempts and the value of the running backs only increases. This makes logical sense, as defenses must respect the quarterback more the better they are, but this does help to confirm the adage in question.

A Bird in the Hand is Worth Two in the Backfield

Correlation doesn't imply causation, but there seems to be some sort of relationship between quarterback rushing and running back rushing value. It actually makes it much easier to predict where added value will come for running backs, that the biggest indicator of running back value is with quarterbacks who keep the ball more. After that, it’s the better your quarterback is at rushing, the better it is for your runners, but volume is our primary indicator.

Before we depart, I did want to look at a specific example that people have talked about this effect in practice, to see if it holds up on a smaller scale as well. This is the case of Washington’s Robert Griffin III and Alfred Morris. The table below shows their 2012 production side-by-side with the 2013 numbers.

Griffin’s rushing attempts dropped about 28% from 2012 to 2013, and not coincidentally Morris’ Rushing NEP plummeted from an acceptable level in 2012 to very subpar. His Rushing NEP per attempt fell a significant 0.05 points per attempt as well. This follows a similar pattern for Carolina’s Cam Newton and DeAngelo Williams, for Michael Vick and LeSean McCoy, and so on.

When a high-volume running quarterback’s volume drops, the defense can spy the running back easier. But if you’re using your quarterback’s full potential to keep a defense honest, that will open up a world of possibilities for your run game. So, progress is good, but we can also play like it’s 1992 again.