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Thursday, October 01, 2009

Jay Jaffe On Defensive Gains And Losses

Jay Jaffe writes about this year's Rangers defensive gains at Baseball Prospectus:
... [Run] prevention is the real story, particularly the fact that the Rangers pulled it off despite a staff which has ranked just 12th in the league in strikeout rate, with 6.3 per nine. The foundation of their improvement has been in the field, where the shift of Young from shortstop to third base to accommodate slick-fielding Elvis Andrus bore fruit—a topic I first explored back in mid-May. After ranking dead last in the majors with a .670 Defensive Efficiency in 2008, they rank second in the AL at .702 this time around, with the majors' second-largest year-to-year improvement....

While that 31-point improvement doesn't top the record-setting 54-point improvement achieved by last year's Rays, it would tie for the eighth-largest year-to-year increase in the Retrosheet era (since 1954), a tidy accomplishment. The improvement isn't solely due to Andrus, who ranks fourth among major league shortstops in Fielding Runs Above Average (+13) and Plus/Minus (+11 runs), and second in UZR (+10.1). Ian Kinsler (+16 FRAA, +7.5 UZR, +16 Plus/Minus) outdoes Andrus by some metrics, and right fielder Nelson Cruz's numbers are particularly off the charts in both FRAA (+21) and UZR (+13), though they weigh in more conservatively at +7 in Plus/Minus. While the magnitude of his contribution may be in doubt, there's no question that Cruz deserves at least some of the credit for the fact that the team ranks sixth in slugging percentage in balls in play after ranking last in 2008, as Matt Swartz noted last week.

"[S]ome regression to the mean is almost inevitable", i.e. this isn't likely to entirely stick; just ask the Rays; but given the personnel changes, Texas is "in good shape to maintain the lion's share of this year's defensive gains".

He analyzes other defenses and notes the Dodgers have improved considerably, as have the Yankees. The Red Sox, though, look pretty bad:

Because they'll have to live with their defense beyond this weekend, it's the Red Sox who are of the most interest from among this group. Shortstop has been the team's Achilles heel; in the absence of Jed Lowrie, they've gotten below-average work from Nick Green, Julio Lugo, and Alex Gonzalez. The team's BABIP since acquiring the supposedly slick-fielding Gonzalez in mid-August has risen from .314 to .325, and that's with the departures of John Smoltz and Brad Penny, who were doing little more than tossing batting practice while in Boston unis. Mike Lowell hasn't been the same since hip surgery, declining by 27 runs according to FRAA, 21.6 according to UZR, and 22 according to Plus/Minus. The outfield's been a problem as well, with Jacoby Ellsbury falling off a whopping 38 runs according to FRAA, 18.6 runs according to UZR, and 14 according to Plus/Minus. Don't even ask about the catching situation, which doesn't figure into Defensive Efficiency, but which rates as a major concern given their upcoming first-round matchup with the fleet-footed Angels.



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