Taking Advantage Of Yankee Stadium

The ESPN park factors for 2009 were released, and Yankee Stadium actually comes in at .965, 20th in baseball. What does that mean? The legend on the ESPN data page explains:

Park Factor compares the rate of stats at home vs. the rate of stats on the road. A rate higher than 1.000 favors the hitter. Below 1.000 favors the pitcher.

Yankee Stadium, after all of the complaining, turned out to be a slight pitchers park in 2009. Breaking the data down further, the new ballpark in the Bronx was a home run haven, with a home run factor of 1.261, good for first in the majors. If so, how was the overall run scoring environment relatively neutral? Tom Tango clarifies:

In a great article in Hardball Times annual, Greg looks at the batted balls at the new Yankee Stadium and Citi. The interesting finding is that while Yankee Stadium turns long flyballs into HR, it also turns almost-long flyballs into outs. Citi field however turns almost-long flyballs into hits. So, this would be an example of where the HR park factor and the Runs park factor on non-HR are not directly related (either unrelated, or inversely-related).

Basically, non-homer extra base hits are suppressed in the new Stadium, as Yankee Stadium is 29th for doubles (.810) and 30th in MLB for triples (.500). Although plenty of balls are leaving the yard, those that stay in the park are turned into outs with enough frequency to give the advantage to the pitchers. The question becomes, can the Yankees somehow leverage this knowledge into a greater home field advantage by stacking the lineup with lefties, taking aim at the short porch in right, and pitching to keep the ball in the larger parts of the park? The aforementioned Greg posted some of his data at BBTF today, and the results, albeit in a small sample, were fascinating:

Home runs hit to right and right-center field at Yankee Stadium, 2009

Before June 1, 2009:
Games: 23
NYY HR/HR per game: 32 / 1.39
Visitor HR: 20 / 0.87
% HR’s by NYY: 61.5%
NYY Home Record: 14-9 / 0.609

On and after June 1, 2009:
Games: 58
NYY HR/HR per game: 67 / 1.16
Visitor HR: 24 / 0.41
% HR’s by NYY: 73.6%
NYY Home Record: 43-15 / 0.741

2009 Regular Season:
Games: 81
NYY HR/HR per game: 99 / 1.22
Visitor HR: 44 / 0.54
% HR’s by NYY: 69.2%
NYY Home Record: 57-24 / 0.704

The Yankees figured out how to clamp down on their opponents’ deep fly balls to right field, while maintaining their own ability to exploit the short porch. This was most likely a combination of more innings being thrown by better and/or healthier pitchers, and conscious effort to steer fly balls towards the deeper left field.

For anyone interested in the stats, if you run a 2-sample Poisson test on the HR rates for the Yankees and their visitors for these two time periods, you get a p-value of 0.03 for the visitors (indicating a strong likelihood of a change in the visitors’ HR rate to RF/RCF before/after June 1st), and a p-value of 0.40 for the Yankees (indicating no significant change in their HR rate). Or in other words, the visitors stopped hitting HR to RF/RCF, but the Yankees didn’t.

The Yankees learned how to leverage the idiosynchrasies of their park, while (unsurprisingly) their visitors did not (or could not). If they hadn’t, the HR totals there would have been even higher than they were…

I find this revelation fascinating. The suggestion is that the Yankees slowly learned the quirks of the park, and eventually were able to turn that knowledge into results. The Red Sox have been using a similar advantage at Fenway Park for years. Hopefully, the Yankees can begin building a serious home field advantage as well.

Photo Credit: Kathy Willens, AP Photo