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Hypothesis: Good Defense Is Good; Bad Defense Is Bad


Defensive efficiency is the percentage of balls put in play that the defense converts into outs — for example, if your team’s defensive efficiency is .750, that means 75% of the balls that opposing hitters put into play result in outs. This statistic is important, and often overlooked. It can often explain an entire pitching staff having better years than anticipated – and by extension, teams doing well beyond the obvious aces and sluggers. Some notable examples are the 2008 Tampa Bay Rays (who lead the majors with a .723 mark), the 2006 Detroit Tigers (tied for second with .716), and of course, the 2005 Chicago White Sox (second in the majors at .725). Defensive efficiency can help you get away with guys who pitch to contact – as opposed to big strikeout pitchers, who are often hard and/or expensive to obtain.

In so many obvious and subtle ways we have noticed that the 2012 White Sox are different from the 2011 White Sox. Part of what drove me insane last year was that not only were Juan Pierre and Alex Rios hitting in an abysmal fashion, they were also garbage defensively. I have nothing but fond memories of Carlos Quentin, but he wasn’t doing the White Sox any favors in the outfield either. The numbers bear out my subjective impression that the 2011 White Sox were a bad defensive team. In fact, they were atrocious, posting the second worst defensive efficiency last year at .697. That’s pretty impressive given that, their offensive skills notwithstanding, Morel, Alexei, and Beckham are high quality defensive infielders.

The 2012 version of the squad is vastly improved, sitting 9th in the majors with a .718 rating. How has this occurred? I’m wary of looking at any single-season defensive metrics for individual players, but we can examine the roster changes. A full season of Alejandro De Aza in center field has allowed Rios to slide back to his natural position in right, where he is clearly more comfortable. With that one tweak it means the team was able to fix huge problems at two positions. Viciedo often takes poor routes to the ball, and he is not the fastest guy in the world, but he is generally very sure-handed and has a plus arm. He has absolutely been an improvement on Pierre – and with de Aza in center he has not had to cover as much ground.

While this statistic isn’t perfect – no defensive metrics are – and there are likely subtle ways that the pitching staff can influence it, the fact is that the White Sox are much improved defensively relative to last year, and the result is a much better team on the whole. By contrast, the Tigers this year are unsurprisingly 4th-worst in the majors at .690, down from a middle-of-the-pack .708 last year. As a general point, when a team is doing better or worse than you might expect, check the defense. After all, baseball is half run scoring, and half run prevention, and every time there isn’t a strike out, walk, or home run, the defense influences the outcome.

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