After the Pirates traded for Wandy Rodriguez, I fully expected to be writing a piece about how he will benefit from moving out of Minute Maid Park as a lefty. And as recently as 2007, I would have been right. According to FanGraphs, the home run factors for right handed hitters in Minute Maid Park from 2002 to 2007 were as follows: 110, 110, 110, 110, 110, and 108 for an average of 109.67. In the same time frame, the home run factors for left handed hitters were: 96, 96, 96, 96, 97, 100 for an average of 96.83. A lower home run factor indicates that a park suppresses home runs and vice versa. Therefore it is clear that from 2002 to 2007 Minute Maid Park greatly increased home runs for right handed batters while slightly suppressing them for left handed batters. This would have made it a nightmare for left handed pitchers.
However from 2008-2011 the home run factors for right handed hitters have been 103, 103, 103, 104 for an average of 103.25. For left handed hitters, they have been 105, 104,104, 104 for an average of 104.25. The average home run factor for right handed batters fell by 6.42 while the same factor for left handed batters rose by 7.42. This is a dramatic shift that I do not have an explanation for.
What is certain is that for the last 4+ years Minute Maid Park has not been as harsh on left handed pitching. Right handed hitters still benefit from hitting in Minute Maid Park (100 is average) regarding home runs, but it is not as extreme as it used to be. A factor of 109/110 (what it was from 2002-2007) would make it comparable to Camden Yards. Now it is comparable to Chase Field.
That said, PNC Park’s home run factor for right handed batters has never risen above 93. As we all know, it is brutal for right handed power hitters. In 2011, only Busch stadium suppressed right handed home runs more. That means that Rodriguez is moving from a park that slightly increases home runs hit against him (as a left handed pitcher) to one that drastically suppresses them. While the change will not be as drastic as I initially thought, Rodriguez’s numbers will benefit from this change in home ballparks.