Andrew Abbott & Defying SIERA
A formula for locating pitchers who are more likely to beat their ERA predictors
The more experience I get doing all of this stuff, the more I’ve come to distrust the #analytics. I still trust them, I guess I’ve just become more willing to work around them. To treat them with NUANCE. I hate the word nuance, it’s almost always the most annoying people in the world using the term, but it’s a good, descriptive word to use.
Here’s the data that inspired this post:
That’s 2023-2025 ERA-SIERA gaps (400 innings pitched minimum). So those would be the ten “luckiest” pitchers in the league if you’re into calling such things “luck”.
There is luck involved here. But man, don’t you notice something when you look at those names?
It’s a whole lot of left-handed pitching, and a whole lot of changeups and curveballs. And I don’t think that’s a coincidence.
When we look at quality of contact against by pitch type and by pitcher hand:
Three pitch types are clearly the toughest to hit. Changeups, sweepers, and splitters. The league has seen an influx of sweepers and splitters in recent years, and we do suspect that unfamiliarity has played a part. But changeups, well, changeups have always been around. They aren’t always the toughest pitch to make contact on, but it is one of the toughest varieties to do real damage on.
And you notice that lefties have a slight advantage in every pitch type except cutters and splitters. It’s a striking difference with curveballs. The right-handed Uncle Charlie goes for a .372 xwOBA when put into play, from lefties, it drops to .358 - a large gap.
We almost must point out the average age of those top ten rule-defiers. Quintana, Kershaw, Verlander, Perez, Wacha, and Kelly were all at least into their mid-thirties while putting up these numbers. That could very well be selection bias. They managed to stay in the league that long because they were doing something right. This isn’t necessarily some lesson to be learned about veteran savvy, but it very well might be.
I’m still not willing to believe that Andrew Abbott can repeat an 11% HR/FB and a .274 BABIP in 2026. But I’m surely willing to believe that he can beat his SIERA by a half run or more again this year. I’m opening my mind, Cincinnati.
So we have some criteria to possibly upgrade pitchers based on. Projections will mostly ignore this potential advantage of being left-handed with a changeup and/or a curveball. The natural thing to do is to look at the top 350 ADP and find those left-handed starters with changeups and/or curveballs!
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