Blame the Park: Power Outage in Minnesota

In 2009 Twins catcher Joe Mauer hit 28 home runs en route to his first career American League MVP award. More than half of his 28 home runs came at home in the Metrodome. This season Mauer, a left-handed hitter, hit only one home run at home in the Twins' new ballpark, Target Field. The shortage of home runs wasn’t limited to left-handed hitters. Right-handed hitter Michael Cuddyer also saw his home run total slashed this season. After hitting 18 home runs at the Metrodome last year, Cuddyer only hit seven home runs at Target Field. Is the ballpark to blame for the power outage in Minnesota?

In the 2011 Bill James Handbook, we calculate park indices for a number of stats, including home runs, that isolate the effect of a ballpark – its dimensions, wall heights, etc. – in order to determine if a park favors the hitters or the pitchers/fielders. A park with an index of exactly 100 is neutral and can be said to have had no effect on that particular stat. An index above 100 means the ballpark favors that statistic. For example, if a park has a home run index of 120, it was 20% easier to hit home runs in that park than the rest of the parks in that team’s league.

Target Field’s park index for home runs in 2010 was 65. That means it was 35 percent harder to hit a home run in Minnesota last year than it was in an average park. That index is the lowest in all of baseball making Target Field the most difficult home run park in baseball last year. That would certainly help to explain the lack of home runs from power hitters like Mauer and Cuddyer, who play their 81 home games there.

One year’s worth of data isn’t enough to fully establish a park as a graveyard for home runs; the next few years will be critical to the establishment of the identity of Target Field. Here’s how Target Field compares to multi-year data for other parks.

Alternatively, multi-year data suggests it is easier to hit a home run in these parks:

* = Data since 2010 ** = Data since 2009

For more on park indices, check out the 2011 Bill James Handbook. The book will be available November 1st and is available for pre-order at ACTASports.com.

Follow us on Twitter!