How Does AT&T Park Affect Hitters?
Color me biased, but there is absolutely no doubt in my mind that AT&T Park is one of the most beautiful stadiums in the game today. Its location and dimensions are practically perfect in my mind, and I honestly can’t think of a ballpark I’d rather sit in to watch a game (aside from, perhaps, Seattle’s SafeCo Field). Naturally, the park holds a very special place in my heart- it is, after all, the home stadium of my favorite Major League team. Within the decade of its existence, it has already seen some historical events: most notably, Barry Bonds’ home run marks and Jonathan Sanchez’s No-Hitter. There are others, of course, but those are the memories that come to mind the quickest for me. I was there for Bonds’ 661st home run; my Father at 756. I was there for the debuts of both Matt Cain and Tim Lincecum. I guess you could say that I have something of an attachment to the park. I have a lot of wonderful memories there, and every time I go to a game my excitement matches that of a child in Disneyland.
This is why I always take offense to the free agents that spurn the Giants’ offers to play for them. Over the past couple of years, multiple high end free agent hitters- the ones that come to mind are Alfonso Soriano, Carlos Lee and Matt Holliday (I’m not sure about Jason Bay or Mark Teixeira)- have made it clear that they had no desire to play in San Francisco. The free agent perhaps most open about his distaste for the park was Adam LaRoche, who declined a rather lucrative two-year deal and wound up signing a smaller one-year deal with the Arizona Diamondbacks. Conversely, pitchers love to pitch at AT&T because of its expansive outfield. This would be great if the Giants weren’t particularly good at developing pitchers- the problem is, they’re quite adept at developing pitchers and the exact opposite when it comes to hitters. AT&T has garnered a reputation as being a severe pitchers’ park; a real death trap for hitters- especially for lefties not named Barry Bonds. But is this true?
One of the beautiful things about sabermetrics is that it gives us tools with which we can begin to test these allegations. In the case of park effects on hitters (or pitchers), we can look at park factors. The concept of a park factor is rather simple: it is often nothing more than the ratio of runs scored at the park in question compared to all other parks in the league, in an attempt to give us a relatively accurate idea as to which parks have higher (or lower) run-scoring environments than others. I’d like to expand on this notion, however, and look not just at the overall park factor- but how the park affects a player’s component batting rates, i.e. how much the park increases or decreases different hit types in addition to non-intentional walks and strikeouts. By doing this, we can look at the way in which AT&T affects right-handed and left-handed hitters differently.
For this little “study,” I’m using five years of data (2005-2009). I looked at the rates of individual offensive events at Mays Field (1B, 2B, 3B, HR, ROE, NIBB, HBP, SO) compared to the rates at all other parks in the National League. The park factor formula I’m using is the one Brandon Heipp outlined in his incredible park factors article, regressed (10%). I would also like to note that all components are regressed the same. This is admittedly not the best way to go about it, but I’m uncertain as to what the “proper” or recommended regression would be (I’ll leave that up to the Mitchel Lichtmans of the world to determine). But, I digress. First, the right-handers:
Overall, we’re looking at a rather subtle effect on right-handed hitters. The park is exactly neutral towards singles, and is essentially neutral with doubles and ROE. Personally, I’m a bit surprised to see the doubles park factor favoring the pitcher- you’d think that a park like AT&T would allow not just more triples, but more doubles as well. This isn’t the case, at least for the righties. All in all, we’re looking at a park that seems to suppress right-handed production. Now, how about those lefties? Do the dimensions of the park affect them differently?
Now we’re beginning to see some more extreme effects. Lefties see a very subtle increase in singles and doubles, with a gigantic leap in triples and an equally devastating drop in home runs. It is also, by my estimations, the most difficult National League park for left-handed hitters to hit home runs. Like righties, we see a very similar decrease in walks and strikeouts for hitters. So, this means lefties are affected more than righties, correct?
If we apply the component park factors to a standard left-handed or right-handed batter’s line and figure the player’s Runs Created*, we can see how much the park influences a player’s overall performance. In other words, can look at the sum rather than the parts. A league average right-handed hitter creates 83 runs in 700 plate appearances in a neutral environment. At AT&T, he creates 80 runs in the same amount of plate appearances. So a player performs at 80/83 = 97% of the league average (80/83 is actually .964; rounding is different). This means that the overall park factor for a right-handed hitter is 0.97. For left-handers? The league average lefty creates 87 runs in 700 PA; at AT&T, he creates 84 runs. Once again, the overall park factor is 0.97. In other words, AT&T Park generally affects left-handed hitters and right-handed hitters the same. The actual difference between the two, if we want to get into specifics, is 0.0005493 in favor of lefties. So…yes, the park absolutely affects a left-handed hitter’s home runs more than a right-hander’s. But the overall effect is virtually no different.
Hitters are absolutely right- AT&T Park certainly does, generally speaking, favor pitchers over hitters. But it’s not a drastic effect by any means, and I don’t think it warrants a hitter demanding the Giants to overpay when bidding for his services. We also have to keep in mind, though, that not all hitters will be affected the same. Barry Bonds still mashed while at AT&T, and some hitters won’t see much of a change (if any) when transitioning to the park. Aubrey Huff is a recent example of this. If you’re a left-handed pull hitter, chances are you won’t see much of a decline in your home run rate- and the same is true for right-handed hitters. And if you’re a left-handed hitter and have a ton of speed, chances are quite good you’ll be seeing a huge jump in triples (Carl Crawford, I hope you’re reading this).