A Super Matchup (Part 1: Passing)

Here, I'm just going to look at the passing games. Clearly, the Broncos' passing offense is better. But that doesn't matter. The Seahawks passing defense is better. But that doesn't matter either. This will be a look into the passing game in today's NFL. And we'll see why it's the Seahawks, not the Broncos, who should be wishing the game were played in a dome.

Normally, the offense dictates the passing game. Good quarterbacks put up good numbers. Peyton Manning dominates pretty much everyone. And good defenses get carved up by good quarterbacks. Nowadays, it's just too hard to stop someone who can consistently make the right read and put the ball on the money. Passing games have taken off. So normally, we should be placing much more weight on the Broncos' offensive strength rather than the Seahawks' defensive advantage.

But these Seahawks are different. It's not just how good they are. It's not just that they allow an average passer rating of 63.4 (The Bengals are second, allowing an average passer rating that's more than 10 points higher.). It's that they have transcended the norm. In the Seahawks' case, the first sentence of the second paragraph doesn't hold.

For a typical defense like the Broncos, the correlation between passer rating allowed and opponent's season passer rating is about .6 (I did the exact calculation, going through each game including postseason and looking at the opponent's starting quarterback's passer rating in the specific game and for the whole season, and r=.605.). Since r^2 = .6^2 = .36, this means that 36% of the variation in an opposing QB's passer rating vs. the Broncos can be explained by the variation in his actual season-long passer rating. Most of the rest of the variation can be attributed to luck*. For the Bengals, r^2 was .18: much lower, but still a reasonably significant factor. However, for the Seahawks, that r^2 value was less than .1 (!). They were so good at defense that the success of their opponent's passing game was almost entirely attributable to luck, and only as important as the Seahawks' own defensive skill.

This leads to a least squares regression line for the Seahawks' passer-rating-against of:
RatingAgainst = .874*opponentSeasonRating - 8.187.
For the Broncos, it's:
RatingAgainst = 1.28*opponentSeasonRating - 21.167
For Peyton Manning, we have:
PasserRating = .6024*opponentSeasonRatingAgainst + 58.8
And finally, for Russell Wilson, we have:
PasserRating = 1.535*opponentSeasonRatingAgainst - 34.1

Each of these, respectively, predict passer ratings of:
Peyton Manning rating of 92.42
Russell Wilson rating of 108.41
Peyton Manning rating of 96.99
Russell Wilson rating of 95.66

Manning's average is 94.7, Wilson's is 102. These predictions not only took into account the skills of the offenses and defenses, but how much each depended on the other team's skill. After doing that, we see that it is in fact the Seahawks that have a huge advantage in the passing game, mainly due to a defense that dominates good quarterbacks almost as well as it dominates bad ones. Given how strongly passer rating correlates with winning, this is a good sign for the Seattle Seahawks.

And it makes sense. Normally, a passing attack involves a set of receivers that more talented secondaries will shut down more effectively. The more solid defensive backs a defense has, the fewer receivers that will be open consistently. Similarly, and more importantly, the more stacked a receiving core is (and the more accurate their QB is), the more consistently those receivers will be open enough against overmatched secondaries. There will always be variance, and as I've talked about many times before, way more of it than most people assume, but an overmatched DB is an overmatched DB, and when the probability of some receiver getting open gets close to 1, the variance decreases. Let's look more closely at this. No defense allows less than a 50% completion percentage, so we don't see the variance drop-off from a lower-than-.5 probability of someone getting open (again, open enough. Because the quarterback matters.). If p is the probability that someone gets open enough for a completion, then the variance of completion percentage is attempts*p*(1-p), which clearly gets smaller as completion percentage (p) increases (again, note that in what we're looking at p is always above .5.). So that's one element. But it's not just that. Every quarterback in the NFL can hit an open slant pretty consistently, and every receiver can get open on a slant reasonably often. This will happen against the Seahawks, too. Because some things are just unstoppable (or at least close). What the Seahawks do with their secondary, which is probably the best secondary of all time, is they take away the stuff that's not unstoppable. Which also happens to be the stuff that separates good passing offenses from bad ones. When every offense is reduced to doing something that every offense does pretty well, the good ones don't stand out any more. And this is probably the bigger reason. Getting open deep against Sherman, Maxwell, Thurmond, or Thomas isn't a sign that you're good. It's just a fluke that happens on a blown coverage a couple times a year, irrespective of how good the receiver or quarterback is. And that's why the Seahawks are such a roadblock for good passing games.

*For a typical quarterback, like Andy Dalton (We were talking about the Bengals, and Peyton and Russell are too good to be considered typical), the correlation between passer rating in a given game and that opponent's passer rating allowed (over the season) is about .3 (This was the calculated r value for Dalton. It was only .25 for Manning.), so only about 9% of the variation is due to defense. That's a fourth as much as the variation due to QB against an average defense like the Broncos.