Adam Wainwright agreed to a one-year contract with the St. Louis Cardinals with a guaranteed $5 million base salary and provisions allowing for up to $5 million more in incentives. Wainwright reportedly was willing to a sign a one-year deal only with the Cardinals. He left a fair amount of money on the table to pitch in St. Louis for another year. Given the righty’s home-road splits last season, one might understand why. Which made me wonder how big the gap was between Wainwright’s pitching at Busch Stadium and on the road.
As a Cardinals fan, you’ve likely heard about Wainwright’s home-road splits. Specifically, how much higher is road ERA was in 2019 than his home ERA. That’s because the gap is quite large. Waino had a 2.56 home ERA and a 6.22 away ERA. Gap? More like canyon.
Despite its flaws, ERA is still a stat of prominence. Defense and scorekeeping inject noise into the stat, so that is not entirely reflective of the pitcher’s individual performance in a given game. So while I still consider ERA, it’s more of a starting point than the end-all, be-all of pitching stats for me.
I like to use Field Independent Pitching (FIP), too, because it focuses on strikeouts, walks, and home runs allowed. These are three things that have far less to do with the fielders and official scorekeeper. They are areas of the game that more reflective of the pitcher’s individual performance (though the catcher, umpire, and occasional fielder will influence them). xFIP takes things a step further by substituting the league-average home run rate for the individual pitcher’s home run rate to illustrate the regression one might expect.
ERA suggests that Wainwright pitched far better at home than on the road. But do the peripherals support this conclusion? The following table includes the component stats of FIP and xFIP.
Wainwright 2019: Home vs. Road
There is no denying that Waino pitched better at Busch than he did on the road. He struck out batters at a slightly higher rate. He walked batters at a lower rate as well. But the difference is far lower than one would expect after looking at his ERA platoon split. The ERA difference of 3.66 is gigantic, while the FIP (0.75) and xFIP (0.50) are far smaller.
We also know that FIP and xFIP are better predictors of future ERA than ERA. That is to say that a pitcher is more likely to post a future ERA closer to his FIP or xFIP than his ERA. Applying this knowledge to Wainwright, he is likely to have better runs-allowed results on the road and worse runs-allowed results at home in 2020 than he did in 2019.
Wainwright’s ERA-FIP gap at home is -1.46 and +1.45 on the road. Based on his strikeouts, walks, and homers allowed, it’s fair to say that Wainwright was about as lucky at Busch as he was unlucky on the road when it came to earned runs allowed. While the future Cardinals Hall-of-Famer pitched better at home than on the road, the difference in his performance was nowhere near as extreme as his ERA split suggests.
Further illuminating why this might be are the rates at which balls in play against the veteran righty resulted in hits and how many base runners crossed the plate.
Each year, MLB averages about a .300 Batting Average on Balls In Play (BABIP). Wainwright held opponents to a BABIP at Busch that was about average, but his road BABIP was far higher. It’s fair to expect that to even out in 2020 so that his road BABIP is closer to .300 than, say, .350.
Fangraphs calculates Left On Base Percentage (LOB%) for pitchers. Typically, 75% is about average. We see that Wainwright was far more successful (some might say lucky) at leaving ducks on the pond when pitching in St. Louis (87.7 LOB%) than on the road (65.4 LOB%). It’s likely that Wainwright’s LOB% at home and on the road will be closer to 75% in 2020. This will reduce his ERA splits.
Too often regression is used as a synonym for “get worse.” But Wainwright’s home and road splits show how regression is a two-way street. We have good reason to believe that Wainwright’s home ERA will regress by going up so that it is closer to his FIP and xFIP and his road ERA will regress by going down so that it is closer to his FIP and xFIP.
We have no reason to believe that he will allow so few runs at Busch Stadium or so many runs on the road. Instead, it seems likely that he will be good at home and slightly worse on the road. In 2020, it’s likely that Waino will once again be an average-ish MLB starter.
The split that Cardinals fans should be more concerned about is how badly Wainwright pitched against lefties as compared to righties. Due to the fact that Wainwright’s curveball is his only above-average MLB offering nowadays, this fact probably shouldn’t be surprising. But what may strike you is just how much better left-handed batsmen performed against the righty than right-handed hitters.
Wainwright 2019: LHB vs. RHB
Wainwright was effective against same-handed batters. But lefties hit him very hard. Perhaps because of how lefties hit for power against him, Wainwright issued walks at a Michael Wacha-esque rate against portside hitters last season. Add the walks and power together, and lefties were lethal against Wainwright last season.
All of this is to say that Wainwright will likely pitch better on the road in 2020 than he did in 2019 and worse at home. But the net effect should even out with respect to his overall performance. Waino’s home-road splits are not cause for much concern.
The splits that are worrisome, however, are Wainwright’s against lefties. It’s a chicken-or-the-egg dynamic when it comes to the interplay between the robust power they displayed against the righty and the walks that he issued. Regardless, Waino’s lefty-righty splits should cause fans far more concerning than his home-road splits.
