Gennaro: Adjusting players’ stats for the quality of their opponents

From SABR member Vince Gennaro at Diamond Dollars on July 30, 2012:

One of the biggest shortcomings in evaluating players’ performance based on their performance statistics (i.e., the outcome of the batter—pitcher matchup) is the uneven quality of opponents that players face. Baseball analysts have made it a priority to adjust for the ballpark in which the players perform, recognizing the profound effect it can have on a player’s accomplishments, as measured by his performance stats. But far less energy has been devoted to adjusting for the quality of the competitors a batter or pitcher face over the course of a season. In the case of ballparks, perhaps the potential effects are more obvious as we watch a 320 foot pop up into the right field corner at Yankee Stadium land in the seats for a home run.

We intuitively know (or the broadcasters will tell us) that in 29 other ballparks the right fielder would have camped under the ball to record a routine out. As a result, park factors have become a common element of baseball analysis and player evaluation. It’s far less obvious (and difficult to measure) that the MLB schedule dictates that some hitters routinely face difficult pitchers, while others face pitchers that are less accomplished. The quality of opponents is even more varied for starting pitchers. Take an unbalanced schedule and match up a starter with an opponent team every 5th day and you’re apt to get an even more skewed distribution of batter-pitcher matchups.

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Originally published: July 30, 2012. Last Updated: July 30, 2012.