Bears Defensive Stats Update

Last week I laid out a simple paradigm for estimating the quality of an NFL defense. I said I was predicting the Bears defense, but really the formula is regression based and therefore backwards looking (like SIERA, for the baseball-inclined) rather than forward looking or predictive (like ZiPS or Oliver, which are actual prediction models).

Anyway, this last Sunday, the Bears defense looked intermittently strong and floppy, but all told, the Bears won despite only moderate help from the offense. So how did the defense do?

Team Y/P Start Point*
Chicago Bears 5.9 34.2 34±7

The terms: Y/P is yard per play. Start is the starting field position for the opposing offense. And Point* (let's call it "points star") will be the shorthand for our nifty little defense estimator. And according to Point*, the Bears defense is still playing like a team that allows somewhere from 27 to 41 points per game. This is a problem.

The Bears currently lead the league in interception rate. That's awesome -- and in no small part due to Kyle Fuller and Chris Conte playing great coverage, as well as an improved pass rush so far headlined by Willie Young. But it's also unsustainable. The Bears got an endzone from Fuller on Monday night that dramatically changed the course of the game. The Jets were driving almost the entire second half. They averaged, as a whole, around 6 yards per play.

Combine that with the tough situation the Bears offense put them in. On average, the Jets started their drives at the 30 yard line. That's a good three yards ahead of the league average. The Bears offense, meanwhile, started at the 23 yard line. The Bears were basically giving a free first down to the Jets every drive.

As I noted before, the Point* inputs basically come from the defense (Y/P) and the offense / special teams (Start). It's not perfect, but nothing about this little toy is meant to be perfect -- or anything but quick and rough. Still, it suggests that both the Bears offense and defense is underperforming with respect to score prevention:

This means too many three-and-outs for the offense and too few sacks and stops from the defense. The Bears are leading the league with a 6.1% interception-rate, but last year the Seahawks led the league with a 5.3% rate. Only one or two teams per year get a rate over 5%, and even then it's never over 6%. Eventually, teams are going to start throwing away from Kyle Fuller or start picking on the depleted safety position. Whatever it is, the Bears cannot rely on clutch picks to bail out an offense going three-and-out every other drive.

Still, despite these problems, Jay Cutler is having an excellent year. The offensive line (which has failed to muster a running game) has protected Cutler well (for a decent 5.5% sack rate, despite throwing every play). And the defense has done enough to win -- despite their injuries and under-production from stars (Lance Briggs, Jared Allen, et al.).

So I'm not worried about the Bears too much, but I do think they have got to make major improvements in order to keep teams from hitting 40 points a game here soon.

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