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Does defense win championships?

Posted by Andrew Mooney  February 3, 2012 01:39 AM

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If you’ve paid attention to the interminable television babble that is this week’s Super Bowl coverage, you’ve probably been forced to confront the following tired cliché at least once: “Defense wins championships.” All season, we’ve heard that the Patriots’ shaky defense will ultimately prevent them from claiming the NFL’s top prize, or perhaps even coming close.

Well, here we are. Both the Patriots and the Green Bay Packers (combined record: 28-4) proved that, in the regular season, defense is hardly a necessity when it’s backed up by an elite offense.

But does this change when the stakes get raised? Perhaps, when the best teams face off in the most important contests, the ability to grind out a defensive victory is particularly valuable. Specifically, does defense win championship games? Using measures of defensive efficiency (DVOA) from Football Outsiders, I analyzed playoff and Super Bowl results from the last 20 years (1992-2011) to determine whether the Patriots are, in fact, doomed this coming Sunday.

I found little reason to fret. In the playoffs, teams with a ranking in defensive efficiency superior to their opponent won games about 53 percent of the time — almost exactly what we’d expect from random chance, given equal teams. The results were similar when limited to just the Super Bowl; just over half (11 out of 20) of the championship-winning teams possessed a better defense than the runners-up, again yielding an inconclusive result.

Further discrediting the adage is the fact that, in this sample of Super Bowls, teams were almost as likely to win while allowing the opposition to outgain them in total yardage. Eight times in the last 20 years, the Super Bowl champions allowed more yards than the runners-up in the big game, and in a few instances, it wasn’t close. On average, those eight teams were outgained by 78.25 yards, the most extreme example of which came in Super Bowl XXXVI; the St. Louis Rams accounted for 427 yards, yet were defeated by some no-name second-year quarterback whose offense only managed 267 yards.

So not only are the defenses’ established identities marginalized, but their in-game performance doesn’t even determine the outcome of the game. Except, that is, for one crucial component: turnovers. As I wrote a couple weeks ago, the occurrence of turnovers is generally unpredictable, but they play a large role in both scoring offense and scoring defense. Only once in the last 20 Super Bowls has a team won the championship despite losing the turnover battle: the Pittsburgh Steelers in Super Bowl XL, who defeated the Seahawks in one of the most contentiously officiated Super Bowls in recent memory.

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Now, this analysis is not particularly rigorous; it does not consider, for instance, the quality of the teams’ offenses or the size of the disparity in defensive efficiency in each game. However, if defense truly were the decisive factor in winning a title, we’d expect to see more compelling results than the ones shown above. There’s just far too much variability in a one-game sample to make any one aspect of the game predictive of the final outcome (see Super Bowl XLII).

Even so, the Patriots are entering uncharted territory. Should they emerge victorious on Sunday, their 30th-ranked defense would be the worst to win a Super Bowl over the period I examined, displacing the 2006 Indianapolis Colts. If it hasn’t already been dispelled, the image of cornerback(!) Julian Edelman raising the Lombardi Trophy would retire this cliché for good.

This blog is not written or edited by Boston.com or the Boston Globe.
The author is solely responsible for the content.

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Stats Driven is powered by David Sabino, who over the last two decades has been a source of statistical analysis on the pages of Sports Illustrated, New York Times, and Chicago Tribune. David has written about all seven recent Boston-area championships for Sports Illustrated Presents commemorative issues, was the creator of such long time features as SI’s Player Value Ranking, NBA Player Rating and long running fantasy football and baseball columns.

He has also authored or made contributions to many books, including the Sports Illustrated’s 100 Fenway: A Fascinating First Century.

Now living in Marblehead, he’s focusing his attention on the Boston sports scene, specifically delving into the numbers affecting the Red Sox, Patriots, Celtics and Bruins, with the goal of informing and entertaining real fans. You can follow him on Twitter at @SabinoSports.

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