On Saturday, the Cardinals signed right-handed starting pitcher Dustin May to a one-year contract with a mutual option. As far as I know, the details of the contract are unknown aside from that. It’s irrelevant anyway in my opinion. If we knew the Cardinals had $20 million to spend, whatever he gets would be relevant. But they are likely to only really sign an outfielder in free agency and maybe a relief pitcher, and it doesn’t really seem like whatever May’s salary is would prevent them from getting the type of outfielder and type of reliever they would spend money on. Whatever those two signings would combine for, it doesn’t seem likely to surpass $20 million, an amount they could rather easily spend.
A frequently cited risk of the Dustin May signing is a health one. May has rarely been a healthy pitcher in his career. He was healthy last year, but the injuries may have taken their toll: His stuff+ declined from 117 to 101, and he’s a much less interesting pitcher if his stuff+ remains at 101. That perceived upside that May brings with his signing vanishes. The upside is his stuff+ reverts back close to career numbers. If that doesn’t happen, I don’t think there’s a ton of upside.
So in light of that, I thought I’d take a look at his injury history, why he’s thrown so few innings in his career, and if there’s reason to think they’ll recur. He has 324 career innings, the majority of which were thrown last season. He never exceeded 56 innings in a season prior to 2025, and ironically, that 56 inning season was the COVID season, in which he was healthy all season.
Near as I can tell, May had no serious injury problems in high school. It is not mentioned in the True Blue LA scouting report on him back in 2016. His weaknesses were his delivery wasn’t consistent and he needed to add weight to his lanky frame. Injuries are not mentioned.
He also did not really have much of an injury history in the minors. He spent time on the injured list for a grand total of 10 days. Having said that, his 2018 season didn’t start until May. I can’t find any evidence why. Teams are not very forthcoming with minor league injuries. He threw 134 innings in 2017, and then 132 innings in 2018. I don’t really know why they would hold back May if not for injury. So maybe there was an injury here, but I can’t find it.
He didn’t have an injury problem in the 2019 season either. He made 20 starts in AAA, and 14 appearances at the MLB level including 4 starts. He threw about 140 innings. In this case, his innings weren’t limited because of an injury but because he was put in the bullpen to finish out the 2019 season. He didn’t get injured in 2020 either. Yeah his innings are low because there were two months of gameplay.
Given his reputation, I am very surprised how spotless his injury history is at this point. Despite being healthy, May was a bit underwhelming in his first “full” season. He did have a 2.53 ERA in 12 appearances, but it was carried by a 19.6 K% and 4.62 FIP. When the 2021 season started, May turned into an ace for five starts. Truly dominant in those five starts with a 37.6 K%. And then he required Tommy John surgery.
The Tommy John surgery explains both 2021 and 2022. With his surgery on May 11th in 2021, May first started appearing in rehab games on July 16th. Fairly normal timetable. He used his entire rehab time and got called up to the majors a month later in mid-August. He was okay in six starts to end the season, with extra rest in every start but his last. In his last, he got blown up and the Dodgers shut him down with lower back tightness to end his season. We’ve hit our first warning signs now. Not a completely smooth recovery from Tommy John. It caused him to miss the 2022 playoffs.
May seemingly had a healthy offseason and stayed healthy to begin the 2023 season. But after nine somewhat unimpressive starts – again weirdly he had a good ERA, but he didn’t strike anyone out – he landed back on the injured list. In July, it was worst case scenario. He had both flexor tendon surgery and a Tommy John revision which knocked him out for the next year. I can’t imagine back-to-back Tommy John surgeries is a good sign.
The next injury, the injury that kept him out of 2024, well this one is as fluky as it gets. While eating dinner with his wife, he swallowed a piece of lettuce that caused a serious tear in his esophagus. He had emergency surgery and his season was done. His 2025 season was mostly healthy, but it did end early. He missed most of September to right elbow neuritis.
On the one hand, because he barely accumulated any innings in his first two seasons for reasons that have nothing to do with injury, one could argue looking at his stat page is misleading as to his injury history. But that 2021 to 2024 run has no such excuse. That’s four seasons with 20 total starts. All the injuries (except the lettuce injury) are in some way connected, although that’s not necessarily a good thing. He has arm and elbow problems that can’t quite heal for four years and then his 2025 season ends early with elbow neuritis?
On top of that it has seriously affected his stuff. His fastball velocity has declined from about 97 mph on average to about 95 mph. The performance on that fastball by results completely tanked, going from +9.4 runs above average in 2023 to -9.3 runs below average. His cutter was also a pretty bad pitch with a .499 wOBA against on 210 pitches. He responded accordingly. He threw some version of a fastball (4-seam, sinker, cutter) about 75% of the time and though the sample isn’t large, he mostly leaned on a bevy of fastballs before 2025. He threw a slider or sweeper about 20% of the time.
In 2025, he upped his sweeper usage to 39%, mainly because it held batters to a .274 wOBA. Sounds promising, but they used to be way better. Understandably leaning on a strikeout pitch more is going to lead to worse numbers. In 2021, his sweeper generated a .000 wOBA on 66 pitches for a 77.8 K%. Okay that’s unfair, that’s the best he’s ever pitched. He wasn’t particularly good in 2020, but his sweeper generated a .208 wOBA and a 50% K rate. His pitch was elite, now it’s okay.
The gamble the Cardinals are making is that recovering from three years of injuries takes some time to build up. That May’s pre-injury stuff will return in some way. Maybe not completely, but better than last season. Either that, or after a season learning how to pitch with diminished stuff, he should naturally improve anyway. If you used to throw 98 and suddenly you throw 94, you can’t pitch the same way. We see he’s already pitching differently. He barely has MLB experience despite reaching 6 years of service; simply getting reps may cause him to get better.
What writing this did for me: I think May staying healthy and good is very, very unlikely. I support the signing, it’s a high reward kind of risk and it’s one year so it’s barely a risk. I’m not trying to throw cold water on this. And I also realize May is unusual, because there aren’t many good comps for him. Most pitchers don’t follow four mostly missing seasons with over 100 innings pitched. Most pitchers who do miss parts of four seasons are not as young as 28. And even with the diminished stuff, his Stuff+ was still 101, so it’s not like we’re dealing with nothing to work with.
But I mean I don’t need to put in a formula to know that a pitcher who had Tommy John, then a Tommy John revision and flexor tendon surgery, returned with diminished stuff and whose season ended due to elbow neuritis – a pitcher being both healthy and good after that, if there are any historical comps at all, is probably less than 10%. It’s a worthwhile gamble, and I want to stress that because I fear me supporting this move is going to get lost here.
This was not really where I was planning to go with the article. But this is where the analysis took me. Lance Lynn’s post TJ surgery was not particularly impressive by advanced stats and it’s why the Cardinals let him leave. The year after he looked more like Lance Lynn (by advanced stats, the ERAs were flipped). He didn’t see a decline in velocity post-TJ, but he did actually throw a bit harder in 2018. Even a little bit harder will probably make a big difference. One thing is for certain: I hope this article ages poorly in 12 months.