Friday, April 07, 2006

Pete Incaviglia Was +5 On The Day

For quite some time now, there has been talk and speculation about major league baseball teams moving on to the next revolution in baseball metrics: the ability to properly quantify defence (I'd provide links, but much of what I have read is unfortunately behind the ESPN Insider wall). While terms like OBP (On Base Percentage) and WHIP (Walks + Hits per Innings Pitched) have become all the rage since the publication of Michael Lewis' Moneyball, many managers have moved beyond this point and are now looking at ways that they can build observably solid defensive rosters. To be honest, since the defensive stuff is starting to trickle down to the mainstream, the best managers (you know who they are) have probably already moved on to the final frontier of pitching metrics. Either way, I hadn't really seen anything on exactly how defense was being measured until today. I had seen bits and pieces, and I suppose if I had looked hard enough I would have found something more substantive, but an article in today's Boston Globe helped sate my curiosity.

In the Globe, Chris Snow breaks down the release of John Dewan's recent book, The Fielding Bible. The focus is obviously on the Red Sox and their defense, but even Bruins fans should find Dewan's system interesting: it's a Plus/Minus evaluation system. Here's how it works:

Baseball Info Solutions records each batted ball's specific direction, distance, speed (soft, medium, hard), and type (grounder, liner, fly, bunt). Direction and distance are computed by clicking a location on a baseball diamond on a computer. The computer then determines how often each type of ball hit to each location at each speed is converted into an out.

If a ball is converted into an out only 25 percent of the time, the expectation that the play will be made is 0.25. If a player makes the play, he is scored a 1.00, minus 0.25 (the expectation that the play will be made), resulting in a score of plus-0.75. If he does not make the play, he is scored a 0, minus 0.25 (the expectation that the play will be made), resulting in a score of minus-0.25.

By adding up all of the credit a player receives or loses for plays he makes or doesn't make, the result is a player's plus-minus.

There is obviously still a certain level of subjectivity involved, as someone has to define whether a ball is hit soft or hard, or whether a check swing was actually a bunt. And there are other limitations, which the article points out. Nevertheless, I find the idea fascinating, as not only does it help quantify a skill too often ignored in today's Rotisserie League baseball culture; it also helps illustrate how simplistic hockey's current indicator of defensive skill, the Plus/Minus System, is. Here's hoping someone is doing the legwork out there on this matter, because I really hate seeing a hockey player rewarded or penalized for simply being on the ice when a goal occurs.


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