What Happens When You Pitch in Texas

The most obvious park-effect variable in baseball is Colorado’s altitude. Okay, nothing to be done about that. No way to pitch around it. The second-most obvious park-effect variable would have to be the Green Monster in Fenway. Boston’s got something no other place has, and it’s right there in left field looming over everything, and last week I took a look at how pitchers attempt to compensate for having that thing in play right behind them. In short, righties get pitched away more often, and lefties get pitched inside more often. It was all very intuitive, but toward the end, I threw in a note about an opposite effect I observed in Texas. Now seemed like as good an opportunity as any to turn that into a post of its own.

Globe Life Park doesn’t have a Green Monster. It doesn’t have any kind of monster, but it does have a justified reputation of being hitter-friendly. There are many culprits, but among them is a frequent gust that’s caused some fly balls to continue to carry out to right and right-center. It’s been referred to as the jetstream effect, and just as Boston is particularly hitter-friendly to left, Texas has historically been more hitter-friendly to right. How have pitchers dealt with that? Well, I guess I already told you.

When I did the Fenway research, I figured that, if I’d be able to find anything, I’d be able to find it in Boston. There’s no denying the existence of the Green Monster, and there’s no denying it has a dramatic effect on a lot of balls in play. The shifts in pitch frequencies observed are somewhat small, but pitch patterns can’t bounce around dramatically, not if pitchers want to remain unpredictable. In Fenway, you can’t exclusively throw righties outside. You just throw outside a little more often, to balance out the ball-in-play distribution.

In Texas, we see opposite changes of similar magnitude. Research was made possible by Baseball Savant, and I decided to look at data from the past three years. This time I just split home plate down the middle. So any given pitch is considered either inside or outside. Sticking with the same format as the post before, let’s look at data, beginning with right-handed hitters:

• Rangers home games: 47.9% pitches over inner half
• Rangers road games: 43.5%
• Difference: +4.4%
• MLB rank: 1st

The numbers should explain themselves — in Texas, right-handed hitters have seen more pitches inside. So they’ve seen fewer pitches outside, and those are the pitches that are easier to drive the other way. As with Boston, the difference might seem small, but it’s also the biggest difference in the game. Now, repeating, this time with left-handed hitters:

• Rangers home games: 67.7% pitches over outer half
• Rangers road games: 63.1%
• Difference: +4.6%
• MLB rank: 1st

You understand. It’s the same explanation. In Texas, lefties have seen more pitches away than they have on the road, because in Texas, those are the pitches more likely to be hit up the middle or toward right. There’s no good part of the ballpark in Texas for pitchers to pitch to, but there’s relative good and relative bad. The shift mirrors the shift we see with righties, more or less.

There’s no real meaningful difference in fastball rates in Texas and in not-Texas. Yet the fastball locations mirror what we see above, which I guess isn’t a surprise at all since fastballs make up the bulk of all pitches thrown. With righties at the plate:

• Rangers home games: 51.7% fastballs over inner half
• Rangers road games: 47.2%

And, with lefties at the plate:

• Rangers home games: 66.1% fastballs over outer half
• Rangers road games: 62.2%

In the Fenway post, I looked at David Ortiz and Dustin Pedroia, individually. Here, let’s consider Adrian Beltre and Yu Darvish. Below, Beltre at home and on the road in 2014. This past season, at home, he saw almost 54% of pitches over the inner half. On the road, the rate dropped to almost 45%. His three-year numbers are about 51% and 45%, respectively.

Beltre is particularly strong, and he’s able to drive pitches over the outer half deep the other way, in the air. It makes sense, then, that in Texas, he’d have fewer opportunities to do that. Now let’s check out Yu Darvish, also in 2014, and only against left-handed hitters so as to make the heat map less confusing. At home against lefties, Darvish threw 71% of pitches away. On the road against lefties, the rate was 57%.

It’s a fairly pronounced shift. In his own ballpark, Darvish didn’t want lefties to get out ahead of his pitches and yank them. This was less of a fear elsewhere. For Darvish’s career, his splits are 68% and 60%, at home and on the road. He also shows a split against righties, although it’s smaller.

A consideration of mine I can’t do anything about: there could be a park effect in the PITCHf/x data itself. If the results in Texas are consistently a little off in one direction, it could make nothing look like something. That’s why I can’t declare anything with 100% certainty, but what I do have on my side is reason; it’s reasonable to think pitchers would try to pitch away from things like this happening:

Yet, one last note about the jetstream: it might no longer be a thing. At least, not to the same extent. Ballpark modifications prior to 2013 might’ve had an effect on the usual wind patterns, and it seems like Texas has been a little less hitter-friendly since. A few people have gone on record noting that certain fly balls haven’t carried as much as expected, so maybe this is an investigation of something that’s not so much of a factor anymore. But, interestingly, the pitch-location shifts have only become larger over time. In 2012, we observe differences of about 2% of pitches. That is, in Rangers home games, righties saw more pitches inside by two percentage points, and lefties saw more pitches outside by two percentage points. The last two years, covering the span since the ballpark was altered, we observe differences of about 6% of pitches, for both righties and lefties. The data would suggest that even if balls don’t carry as well to right anymore, pitchers still pitch like it’s a danger zone. So either they’re wrong, or the jetstream is still present.

If it’s all an irritating PITCHf/x park effect, where the data is erroneous, welp, that’s too bad. And a little embarrassing! But at least, if this is all true, it makes sense why it would be true. It makes sense why pitchers would pitch away from the Green Monster, and it makes sense why pitchers would pitch away from Globe Life’s right and right-center fields. No, the differences aren’t dramatic. No, the differences will never be dramatic. But, park effects can have park effects. It’s pretty swell to see how pitchers respond to the environment around them.