Is Michael Wacha actually injury-prone?

Michael Wacha was drafted 19th overall by the Cardinals in June of 2012. Just over a year later, after tearing through the minors, Wacha arrived in St. Louis looking like a future front-line starter. He was big, threw hard, and had an absolute wipeout changeup. In his first 185 MLB innings (including 30 excellent playoff innings) stretching from 2013 into 2014, Wacha was brilliant, with a FIP in the low threes and ERA below three.

Then, as so many young pitchers do, he got hurt. On June 22, 2014, Wacha was placed on the DL with a sore right shoulder.

The underlying injury was rare: a stress reaction in his scapula, helpfully detailed at length in a Beyond The Box Score piece by Stuart Wallace. Ominously, the injury was compared to one that has nagged Brandon McCarthy — another tall, hard-throwing righty — for years. In McCarthy’s case, the condition ultimately led to repeated stress fractures in his scapula. As a result, McCarthy has managed to make 30 starts only one season in his 13-year MLB career, and over 20 starts only three other times.

So, naturally, Wacha’s 2014 shoulder injury raised serious (and legitimate) concerns; when you have a pitcher with the same shoulder condition that Brandon McCarthy has, you’d better be worried. There was some reason for hope, though. McCarthy’s condition progressed years ago to the point where it was actually caused stress fractures in his scapula, but Wacha’s had not yet reached that point by the time it was diagnosed. Because (as Wallace notes in the post linked above) rest is adequate treatment for a condition like Wacha’s, the Cardinals hoped that Wacha’s shoulder could be managed in a way that would still allow him to handle a starter’s workload.

So far, they’ve been right. Or at least mostly right.

Wacha made 30 starts in both 2015 and 2017. In 2016, though, the shoulder issue did flare up — but not until August, which allowed Wacha to make a reasonable 24 starts. So in the three full seasons since Wacha’s condition was first diagnosed, he has made an average of 28 starts per season. That’s not the most durable pitcher in the league or anything, but well... that’s pretty good, isn’t it?

Although the 2014 and 2016 DL stints lead to an obvious challenge to this post’s premise — how can I be saying Wacha’s shoulder condition does not make him injury-prone when he’s missed significant time twice due to it? — the fact is, Wacha’s innings totals compare not-unfavorably to most starting pitchers. Over the last three seasons, Wacha has made 84 starts. That’s six more than David Price, three fewer than Justin Verlander, three more than Clayton Kershaw, four more than Sonny Gray, two fewer than CC Sabathia, two fewer than Kyle Hendricks, two more than Ubaldo Jimenez, two fewer than Cole Hamels... you get it. These are guys who have not been without their dings and dead arms, but none of them are guys with reputations for fragility. They’re just pitchers: they throw a ball as hard as their arms can take it for a living, and sometimes they get hurt.

Objectively, based on actual number of times a pitcher takes the mound, it doesn’t appear that we ought to label Wacha much less durable than the ordinary starting pitcher. At least not the version of Wacha we’ve seen the last three years, with a known scapula problem that the team is helping him handle. That doesn’t mean he’s not an injury risk. Rather, it means that the ordinary pitcher is an injury risk. Knowing that Michael Wacha faces a particular type of risk doesn’t necessarily mean he’s riskier than ordinary, it just means we happen to know which particular part of his body dislikes its owner’s chosen profession the most. Kind of like Clayton Kershaw’s back, or David Price’s elbow. Kind of like Pitcher X’s whatever, that we never find out about until the day we do.

Still, it’s too facile to simply count up starts and call it a day. For one thing, Wacha’s innings total over the past three years is lower than most of the comps listed above. One explanation is that an inclination to quick hooks is a conscious part of the Cards’ management of Wacha’s shoulder, and it would be fair to count that as a minus in the durability column. Another explanation is that for whatever reason, Wacha’s been especially bad the third time through the lineup relative to his baseline — that’s true, as he’s been an above-average pitcher overall but his .356 wOBA allowed (2015-17) is below the average NL third-time-through wOBA of .339 over that stretch. Again, this apparent lack of staying power within starts could be called a type of non-durability.

Those are fair points. However, it’s also true as a general matter that pulling starters on the earlier side is better, and is an idea that the most progressive organizations (hello, Astros) have begun to embrace even in the regular season. So if Michael Wacha has ordinary durability in terms of taking the mound every fifth day, but below-average durability in terms of going deep into games... maybe the right question is “who cares.”

A final point: it’s possible that there’s a mechanical solution to Wacha’s condition, and it’s possible that the Cardinals are onto it. I’m not a pitching mechanics expert, nor am I a person who pretends to be one online for attention. But in the BTB piece I linked above, Stuart Wallace noted the extreme “over the top” delivery exhibited by both McCarthy and Wacha, and highlighted the change in McCarthy’s release point over the years:

Note that McCarthy’s release point became notably less over-the-top as his shoulder degraded — and recall that he actually had stress fractures in his scapula, unlike Wacha who merely has the precursor condition. Now here’s Wacha:

I’m just spitballing here, but: McCarthy messed his shoulder up permanently when his release point was maximally over-the-top. Wacha initially threw much the same way, then got hurt. He came back in 2015 with a slightly lower and more sidearmed release point, and was fine. But then in 2016 it had crept back toward 2013-14 levels... and he got hurt again. Then 2017, back down and out it went, and he was fine again.

Nobody should do analysis this shallow and claim that they’ve “solved” anything. So I’m definitively not making that claim. But here’s the data we have: the Cardinals know about Michael Wacha’s scapula problem. Since they learned about it, Wacha’s been pretty average in terms of durability. And his more-durable seasons happen to coincide with observable mechanical differences — the kind of thing a coaching staff is well-equipped to monitor and help him with.

Maybe that’s something, maybe it’s nothing. But it’s certainly interesting.