Are Diamondbacks Pitchers Afraid of Chase Field?

The Diamondbacks have been terrible at Chase Field this year. It’s kind of hard to figure out why, at least if you apply the standard thinking that the team gets to enjoy a spacious, hitter-friendly ballpark to pile up runs in 81 times per year. As we’ve said a million times now, Chase is not Coors, but it’s the next closest thing and you’d expect the drop off to work the other way if there’s anything to take away from the Rockies. Instead, it’s been the opposite as the team has enjoyed big success on the road but seemingly can’t get out it’s own way at home. The problem hasn’t been run-scoring, but rather run prevention.

At Chase, the D-backs have racked up 4.38 runs per game. They’ve scored 4.6 per game on the road, but that’s influenced by playing at Coors Field in wacky games that aren’t fit for human consumption. Pulling games in Denver out of the equation, the team has scored 4.0 runs per game on the non-Coors road. So maybe there is a little drop-off away from Chase for the offense, but it’s nothing like the changes we’ve seen on the pitching side. On the road, the team has allowed 4.25 runs per game. If we want to pull Coors Field from those numbers, it’s down to 3.73 runs per game. At home, in Chase, the team’s surrendered 5.5 runs per game. That’s not a typo. They’ve given up nearly two more runs per game at home than on the road (sans Coors) while scoring just 0.38 more runs per game.

At some point, you have wonder what gives. We know Chase Field sucks for pitchers but this is something else. It’s hard to be this bad at home and still be competitive. One way the results could be skewed is if some pitchers have had an uneven distribution of starts at home or on the road. That’s worth looking into. Let’s say Robbie Ray has made almost all of his starts at home while Zack Greinke has pitched almost exclusively on the road. That would make a difference. Here’s how things have broken down through Tuesday:

That doesn’t look wildly out of balance to me. The only guy with a big split is Greinke and he’s made more starts at home and been pretty good in more than half of them. Shelby Miller’s been perfectly balanced. I’m comfortable saying that the distribution of starts isn’t necessarily what’s behind these big splits.

Pitching in the strike zone is a good thing… until it isn’t. There’s a break-even point, and once you pass it, you start doing more harm than good. We tend to think of balls as bad pitches, but truth be told, it’s important to miss, especially when a pitcher has the ability to miss where he wants to. If everything were over the plate, it’s not hard to imagine what would happen to a lot of those baseballs. We don’t know exactly where that break-even point is, but it’s something like 65%, give or take. On the road, the Diamondbacks have thrown 61.8% of their pitches for strikes, good for a 19.6% strikeout rate and a 9.3% walk rate. On the road, not stripping out Coors (because I don’t have a non-Coors split handy), the rate of strikes jumps to 63.0%, jumping the strikeout rate to 20.5% and dropping the walk rate to 8.9%. My guess is that if I could strip out the seven contests at Coors Field, this discrepancy would grow by a decent margin.

The differences above are small, sure, but they might highlight something unique: Diamondback pitchers could be more reluctant to come over the plate when pitching at home. It’s not hard to figure out why they might feel this way. Batters hit 2.5% more fly balls at Chase Field off of D-backs pitchers (opposed to on the road, including Coors) as they deliberately try to take advantage of the thin air in Arizona. Of those fly balls, 15.5% become fly balls at home and only 11% become home runs on the road (again, including games at Coors Field). Stripping away games played in Colorado would magnify this effect, just like above, but you get the feeling that the staff could become gunshy considering what happens when they pitch at home.

It’s hard to say for sure why the team is less willing to come over the plate at home, or if that’s even the case. Correlation does not equal causation and this could just be random noise. But considering what we know about Chase Field and using some logic, it wouldn’t be surprising to see this staff take two different approaches to getting their work in. If batters were going to hit more fly balls against me at home and those fly balls were almost 30% more likely to leave the yard than the one’s I yielded on the road, well you can rest assured that I’d try to serve up fewer baseballs to be taken advantage of. Of course, that means fewer strikeouts, more walks and the balls still leave the yard at alarming rates. I don’t know, it just sounds like a shitty situation, to be honest, one that’s tough to find your way out of.

So while Arizona struggles at home, know that it’s not the offense dragging them down. They do score fewer runs on the road than at home, but that’s outpaced by the discrepancy in runs surrendered by a large margin. Pitchers aren’t coming over the plate as often at home and they’re still paying a steep exchange rate. Let this be a reminder that life is hard at Chase Field, in case you hadn’t noticed. In a year when Lamb is the GOAT and life is confusing, the horrors of Chase Field remain the same.