Jeff Hughes | July 11th, 2016

Another guest column from the artist known as Data.

Every offseason (and throughout most seasons) there’s a lot of talk amongst Bears fans about whether or not the Bears can win with Jay Cutler as their quarterback. Today I’m going to attempt to answer that question by looking at Cutler’s peers around the league.

I identified five players who are, statistically speaking, Cutler’s peers: Carson Palmer, Matthew Stafford, Eli Manning, Joe Flacco, and Alex Smith. Including Cutler, these six quarterbacks all have started at least 90 games, thrown at least 3500 passes, and posted passer ratings between 83.5 and 88.1.

Basically, they’ve all been around for a while performing, as a whole, at an average to above average level.

Cutler is smack dab in the middle of the group with 134 starts (3rd), 4354 passes (3rd), and an 86.0 passer rating (2nd).

It turns out you can, in fact, win with a quarterback of that caliber. As a whole, these 6 QBs are 432-379-1 in games they start, which averages out to about 8.5 wins per season. Of the 50 seasons in which these quarterbacks have thrown 300+ passes, 20 have resulted in playoff berths, while 2 more have featured 10 win seasons-the typical threshold for the playoffs-with no postseason. These quarterbacks win more than they lose and their teams perform well enough to make the playoffs nearly half the time.

Despite their similar individual statistical resumes, the team success these 6 quarterbacks experience has varied tremendously. Their career win percentages in games they start varies from 45% (Stafford) to 61% (Flacco), and their rate of making the playoffs ranges from 11% (Cutler) to 75% (Flacco).

What causes these differences?

I looked at three potential factors: individual performance, team offensive performance, and team defensive performance.

Individual performance was measured through passer rating, an admittedly imperfect metric that still gives something of an idea of how well a quarterback performed that year. Since league-average passer ratings have changed from the low to mid 80s to the low 90s in the past 10 years, I looked at a quarterback’s rank among qualified passers within a season. I also looked at interception percentage on a season, since you could argue quarterbacks turning the ball over are more detrimental than what shows up in total passing stats. For offensive and defensive performance, I used a teams’ rank in Football Outsiders’ DVOA, which is widely regarded as one of the better metrics for evaluating a unit.

I examined win percentage against those 4 metrics for all 50 seasons with those six quarterbacks and found some interesting results. Offensive performance and team success had a correlation of only 0.22, meaning there was very little relationship between the two (it’s on a scale of 0 to 1, with 1 being a strong relationship). Individual quarterback performance was a bit stronger, but still low, with correlation values of 0.37 for interception percentage and 0.40 for passer rating rank.

When we look at defensive performance, however, we see a different story. The correlation there was 0.64, significantly higher than any of the offensive factors.

Looking at each quarterback’s career win percentage against career averages in those categories makes that trend even more distinct. The correlation between team success and defensive rank comes in at 0.66, while those for team success and offensive rank (0.25), passer rating rank (0.28), and interception percentage (0.31) all come in less than half that high.

The lesson here is clear. If you want to build a consistent winner with a quarterback of this caliber, you do it by building a consistently good defense.

Of the 50 seasons these quarterbacks have thrown 300+ passes, their teams’ defense has ranked in the top ten 17 times. In those 17 seasons, teams are 171-88 (0.67) when their starting QB starts the game and have made the playoffs 12 times. By contrast, teams from the same group with bottom 10 defenses are 71-113 (0.39) with 0 playoff appearances in 13 seasons.

This same massive split does not happen with offenses. There top 10 units are 144-105 (0.58) with 8 playoff appearances in 16 seasons, while bottom 10 units are 53-50 (0.51) with 3 playoff appearances in 7 attempts. It should come as no surprise to learn that those 3 playoff seasons all featured top 5 defenses.

Now this isn’t to say that offensive performance is completely irrelevant when you have a good-but-not-great quarterback. General managers and coaches should still work to field a quality offense. But the data overwhelmingly suggests that the main focus should be on building the defense, as this has a greater impact on winning games.

Looking back at my original question, it is clear that the Bears can in fact win with a quarterback like Jay Cutler. Even better news for Ryan Pace and John Fox is that the blueprint for doing so is clear: pair him with a strong defense and good things will follow