Does Adam Wainwright Really Pitch Better At Home?

Ahead of the Division Series against the Braves, the Cardinals had the option of starting Adam Wainwright in the opener on regular rest, but the team opted to start Miles Mikolas instead. With Jack Flaherty locked into Game 2, Wainwright started the third game of the series and pitched a gem at home. Fast forward to the NLCS, the Cardinals again could have opted to start Wainwright in the first game of the series, but again opted for Mikolas, lining Wainwright up for potentially two starts at home in Games Two and Six. It is certainly possible that starting Mikolas ahead of Wainwright is simply the better choice, but it also might feel like getting Wainwright more starts at home is a savvy choice because of his fairly massive splits home and away.

In games started at Busch Stadium this year, Wainwright has a 2.56 ERA. That’s significantly lower than his road ERA of 6.22. The results have been markedly different, and the gap is large enough that we might think Adam Wainwright has pitched a lot worse on the road this season. Even his FIP, which is 4.77 on the road and 4.02 at home, suggests there might be something happening that requires examination. Wainwright had this to say about pitching better at home on Friday:

I don’t know if there’s a dead set reason, other than I just like pitching at home. But there’s been years where I pitched better on the road, too, than I did at home. And guys were asking me the same questions the other way around. Why would a talented pitcher like [Mike] Soroka pitch much better on the road? Sometimes it, just weird things happen like that in baseball. Sometimes there’s a reason, sometimes there’s no rhyme or reason. Sometimes it’s matchups, sometimes it’s — I don’t know what sometimes it else could be. But baseball has a way of correcting itself. Who knows, it might come back next year and be 16-0 on the road. We’ll see.

Wainwright went with an answer that implies that he thinks it’s random. But we can go a step further, and argue that Wainwright hasn’t even really pitched worse on the road than at home for a large part of the season. Immediately, we can shrink the huge ERA gap by noting the much smaller FIP differential. Wainwright’s BABIP at home this season was a normal .299, but on the road, it was .344. Given he was playing in front of the exact same defense, there isn’t much of a reasonable explanation other than luck. In addition, Wainwright’s left-on-base rate at home was an absurdly high 88%, while on the road, it was a very low 65%. To think Wainwright could control sequencing and the ability to pitch with runners on base at home but not the road feels like a bit of a stretch.

However, even if we accept his FIP, there’s still a three-quarters of a run gap between his performance at Busch and his games elsewhere. We can close some of that gap by noting that all pitchers do better at home than on the road. This season, National League starting pitchers put up a 4.24 FIP at home and a 4.54 FIP on the road. Applying this same information to Wainwright, we would come up with a 4.21 FIP at home and 4.51 on the road. If we add a park adjustment to account for Busch Stadium being pitcher friendly, we basically end up at Wainwright’s actual home FIP and just a couple tenths away from his road FIP.

That differential is backed up Wainwright’s xwOBA as well. At home, Wainwright’s xwOBA this season was .318; on the road it was .337. Starting pitchers in the NL had a 15-point differential between their home and road xwOBAs in 2019, almost the exact same home/road differential as Wainwright. The difference in results, then, is just a mix of defensive randomness, luck, and the ballpark. If we look at more recent performance, the difference between home and road fade even more.

On June 1, Wainwright had made 11 starts with a 4.86 FIP and 4.94 ERA. In other words, he wasn’t pitching that well, though his home starts were much better than his away ones. Since that time, he has made 20 starts, with 11 coming at home and nine on the road. Overall, he’s pitched pretty well during that time, with a 4.10 FIP and 3.81 ERA. At home, his FIP 4.11, while on the road it is 4.07. He’s been essentially the same pitcher for the last four months on the road and at home. The ERA differential is still there, but that’s mostly luck. His xwOBAs home and away during that time are within 15 points of each other. There’s just not any substantive evidence to suggest that Adam Wainwright is actually a different pitcher at home compared to on the road.

Getting Adam Wainwright more home starts isn’t actually hurting the team, as moving him and Miles Mikolas doesn’t make a difference in their chances of winning. As fan service goes, giving the 38-year-old Cardinals legend more home starts is definitely a plus. And it’s likely a comfort for Wainwright and the Cardinals to know that if he were to get a road start, there’s not much reason to think he would pitch any worse than he should be expected to when in St. Louis. Of course, if Wainwright does get the opportunity to make a road start, it likely means he pitched well in two more home starts, a feat sure to grow this false narrative to even greater proportions.