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Fact Check: Backup Quarterbacks are Important!

Philadelphia Eagles v Houston Texans Photo by Thomas B. Shea/Getty Images

I think by now it’s common knowledge that the NFL is a passing league. But allow me to belabor the point. Since 1989:

• The average team passing yards per game increased from 210.9 to 241.5 (2016).

• Team passing touchdowns have increased from 1.2 per game to about 1.6.

• Team passing attempts per game increased from 31 to 35.7 in each of the last two seasons.

And yet, despite the increased number in team passing attempts, team interceptions per game decreased from 1.2 to 0.8. On the surface that may not seem significant, but over an entire season it translates to about 200 less interceptions league-wide than there were 28 years ago. Given all of this, is it surprising the Eagles have shelled out lucrative contracts to backup quarterbacks? Turns out, yes.

This wasn’t my initial thought, mind you. I figured, since the NFL places a premium on QB play and injuries at the position can derail a season, spending a lot of money (relatively speaking) on a quality backup should pay dividends.

Our friend Sean Cottrell agreed (h/t for the post idea). What follows, I thought, would just validate how smart we are: Of course teams with pricey backups win more games than those with cheap ones. No brainer.


Quarterback Injury

First, in order to get a handle on the impact QB injuries have on the game, I compared Football Outsiders’ Adjusted Games Lost to injury (AGL) for quarterbacks to team wins. A linear regression analysis showed no relationship (r-squared = .09). I took this to mean that starting QBs play pretty consistently, even when injured, and backup QBs do a decent job of carrying the torch when starters go down. So maybe, just maybe, there’s something to paying backup QBs well.

But does experience matter?

Presumably, backup QBs with more lucrative contracts are those with more experience in the league, like Chase Daniel and Nick Foles. I used the same linear regression technique as above to compare backup QB experience (in years) to team wins, and found… nothing (r-squared = -.15). Well, not nothing, just that more experience doesn’t really matter all that much (see, Dak Prescott). BUT, maybe there’s some kind of relationship between backup QB experience and how a team performs relative to what’s expected (Pythagorean wins). In fact, yes, logistic regression tells us that experience matters, just not how you’d expect. For every one year increase in a backup QB’s experience (league average is six years) a team is 20% less likely to perform better than expected.

What about salary?

If backup QB experience wasn’t what I thought it was then maybe how much a team pays them is. Well, kind of. Again, just not how I expected. There’s a slight negative linear relationship between backup QB salary and team wins (r-squared = -.28): as backup QB salaries decrease, team wins increase (and vice versa, for you causation is not correlation folks). Again, slightly. So I turned to logistic regression to compare backup QB salary to how a team performs relative to expectations, just as I did with QB experience above. Here, the relationship is more pronounced: for every one million dollars a team pays in backup QB salary (league average is $2.5M), a team is 40% less likely to perform better than expected.

What’s all this mean?

Well, it means that Sean and I aren’t as smart as we thought. On average, teams that have less experienced, cheaper backup QBs tend to win more games than those that allocate more money for more experienced ones. When you look at the current landscape of the NFL, it seems to make sense. Dak Prescott, Jimmy Garoppolo, and Landry Jones are all younger quarterbacks forced to play for good teams, and they performed well. But these are also good teams with high-end-if-not elite starting QBs, so there are definitely more factors at play than examined here, factors that impact team expectations and salary allocation.

For the Eagles, the good news is Nick Foles’ salary counts as $1.6M against the cap this season, well below the league average. Bad news is, Foles will be a more experienced, much pricier backup option next season. Maybe the team will do something about that.

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