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October 6, 2009

Playoff Prospectus

Post-Season Ballparks

by Clay Davenport

A park factor, as used here, is a measure of how a team's home field changes their statistics. It results from a combination of many factors—the distance and height of the outfield fences, angles, foul territory, visibility, field surface, and weather, to name a few. It is not the case that the Yankees have a high park factor for home runs (PF) because the Yankees hit a lot of home runs. To get a high PF, you need to hit and allow more home runs in your home games than you do in your road games. An average effect on HR is written as '100'; a better-than-average park will score something like 120, which means they get a boost 20 percent above average, while a poor hitters' park would score 90, or 10 percent below average. Players are also graded on who has the best and worst fit to their stadium—not on how well they hit home/road, but how well their profile matches or doesn't match what the park gives.

New York Yankees and Yankee Stadium 2: A lot was written early in the season about how much the new Yankee Stadium was increasing home runs, and deservingly so—the new digs were the best home-run park in the majors, with a 125 Park Factor, or 25 percent better than an average (or neutral) PF. Not everything written was accurate, though. Early reporting focused on how well left-handed hitters were doing, describing a "wind tunnel" to right, but right-handed hitters actually benefited more (136) than lefties (117). We saw a drop-off as the year went on, from a remarkable 158 PF in April to an ordinary 97 in September; how much of that was due to some real change (since wind patterns do change with the seasons) or pitchers learning to cope with the new digs, we don't really know yet. The focus on home runs obscures the fact that it was the absolute worst place in the majors for hitting triples (PF 49) and the second-worst place to hit doubles (80; San Diego had a 77); the net result is that it was a pretty average park for overall run scoring. It does favor sluggers, the more one-dimensional the better, and does not have a strong left/right bias. Hideki Matsui, Jorge Posada, and Alex Rodriguez all had Equivalent Averages about ten points better than their adjusted park-neutral stats, while Derek Jeter, Robinson Cano, and Brett Gardner each lost about five points from the same adjustment. The Tigers who should benefit most would be Miguel Cabrera and Brandon Inge, while Gerald Laird and Adam Everett look least capable. Among the Twins, Justin Morneau, Michael Cuddyer, and Joe Mauer all get about a 10-point gain in EqA; Carlos Gomez, Orlando Cabrera, and Denard Span all take big hits.

Detroit Tigers and Comerica Park: Comerica was a neutral park overall, with the only noteworthy feature being that it's a good place for triples (115 PF). That masks a huge split, as right-handed hitters did better than lefties across the board, with better PFs for singles (99/96), doubles (101/92), triples (165/92), home runs (110/88), and Equivalent Runs (112/86).They also had advantages in walks (110/103) and strikeouts (94/107, and in this instance lower means better for the hitter), which all together suggests a visibility problem from the left-hand side of the plate. The difference in EqA made for a 105 PF for righties and 93 for lefties, and was the largest such split in baseball. Curtis Granderson, the Tigers' only full-time lefty in the lineup, got clobbered by the park this year, not that it did Clete Thomas or Aubrey Huff any favors either; Ryan Raburn, Marcus Thames, and Brandon Inge did very well. As far as potential Yankee effects, Alex Rodriguez should love it, and Derek Jeter should also do well. The rest of the lineup is either left-handed or switch-hits, and will be facing a mostly right-handed staff (the Tigers should make sure Washburn starts on the road), which means they'll be batting left and suffering for it.

Minnesota Twins and the Metrodome: The home of the hefty bag rates as one of the league's better hitting parks, with a mild advantage going to left-handed hitters. Singles and triples are especially elevated, and the stolen-base factor (174) is the highest in the majors. We don't normally think of steals as something with a strong park effect, beyond the fact that teams tend to run more in low-scoring parks and less in high-scoring parks; since Minnesota is a good run environment that shouldn't matter. The picture is one that benefits speedy guys most, and the best Twin to fit the park was Denard Span; Cuddyer and Joe Crede were hurt the most. The biggest Yankee beneficiary of what the Metrodome offers should be Brett Gardner, although most Yankees will benefit somewhat. The only real loser is Alex Rodriguez.

Los Angeles Angels of Anaheim and Angel Stadium: The Big A of A rated as the fourth-best home-run park in the majors this year, at 120; since you don't expect the weather to cool off as much in LA as elsewhere, that number should stay up in October. Double and triple rates were low, at 92 and 61; the overall effect is to give a small edge to the hitters, and within that, a lean towards right-handed hitters. The differences between the best and worst-fitting hitters wasn't large—Juan Rivera and Mike Napoli were helped a little more than the rest, while Erick Aybar and Chone Figgins suffered the most, but everyone was within 10 points of the EqA of their park-neutral stats. The Red Sox, meanwhile, are very well constructed to take advantage of the park; Jason Bay, Kevin Youkilis, David Ortiz, and Victor Martinez all fit Anaheim a lot better than they do Fenway.