07.29.07
Defensive Growth
The Red Sox have allowed only 3.94 runs per game this year, a marked improvement from their mediocre 5.09 mark set last year. Much of the credit is due the pitching; Beckett has shown better command, while both Matsuzaka and Okajima have played key roles. Yet even the best pitchers rely on their defense to make the plays, and the Red Sox growth defensively has contributed to their success at run prevention.
Defensive skill is commonly measured by “errors”, however an error is rarely scored on a ball the fielder fails to reach. The league leaders in fielding percentage are often players with soft hands but very limited mobility, making it a very poor measure of effectiveness. Range Factor is perhaps slightly better, counting the number of plays converted successfully, yet it is a poor tool for assessing a team. After all, there are only 27 outs to go around and somebody has to convert the putout. Neither does it differentiate between fielding a batted ball (hard!) and catching a thrown ball (easy!). A first-baseman who plays in front of a ground-ball pitching staff could be expected to lead the league in Range Factor simply by standing on the bag to receive throws.
The best commonly available defensive measure is Zone Rating, a percentage of the balls hit to a player’s typical “defensive zone” that are converted for outs. It isn’t perfect by any stretch of the imagination; there are significant park factors, especially for outfielders, and it does not sufficiently reward players with exceptional range who go “outside their zone” to make plays. Still, a player with a strong Zone Rating over the course of a full season can be presumed to be strong defensively and a player with a very weak Zone Rating likely does not belong at his position. I will also cite Defensive Rating, a normalized statistic (100 = league average) calculated by Baseball Prospectus. These statistics will tell largely the same story, though some discrepancies can be expected.
So how have the Red Sox fielders fared this year? Read the rest of this entry »
Over the last two years we’ve already observed some moderation in the number of miles driven. Both the number of licensed drivers and the GDP have steadily increased, yet the miles driven have leveled off. The truncated summer peak you observe in the chart to the right suggests that people might be reducing their discretionary miles.