The Case For Casey Mize

Years after the original hype, Casey Mize still has a promising future.

Casey Mize has a bit of a reputation problem. Not through any fault of his own, there’s no off-the-field issues, no public outcry over questionable behavior, nothing like that. Rather, he’s a victim of circumstance. Being named the #1 prospect in baseball comes with crushing expectations. That was the position Mize found himself in five years ago, a year removed from being the first overall pick in the 2018 draft. The sports business is a brutal and unforgiving world, the moment you’re labeled as the next big thing, there’s an aura that encompasses you. If you don’t live up to what everyone wants you to be in a timely manner, the aura sours and quickly becomes a stigma. 

Mize struggled in his first chance in 2020 but earned a full-time rotation spot in 2021. He made the most of it, posting solid results, a 3.71 ERA across 150 innings. This came with a caveat, however. His underlying numbers were nowhere near as good as the outcomes. He had middling strikeout and walk rates, and his batted ball profile wasn’t particularly promising either. Going into 2022 there were a lot of questions around whether or not he would take the next step. We didn’t get the chance to find out. He got through two mediocre outings before being put on the IL with an elbow sprain. A month later he went under the knife for Tommy John surgery.

Here we are now, nearly 22 months later, talking about the pitcher that was promised once again. He’s made some waves since showing up to Spring Training throwing as hard as ever with some changes to his arsenal. At this stage of both his development and his recovery from injury, the results are less important than the process. Let’s break down what he has to offer and why there’s still reason to be optimistic about his future. As was done with the previous article, I’ll be using both 2024 spring training data along with regular season data to get a larger sample to work with.


The Fastball


Mize’s fastball is the pitch that’s seen the most change since his return from injury. What was previously a fairly average but somewhat interesting fastball has jumped to distinctly above average in its shape. So far, he’s averaging 95.2 mph, with 17.8” of IVB, and 8.1” of HB, from a slightly lower-than-average release height of 5.8’. This also comes with the bonus of 7.2’ of extension on release. His old fastball was more than a full tick slower, with less vertical movement but from a lower release. I believe he made a mechanical change that allows him to get behind the ball better and get more efficient spin.

This is a really solid base to build an arsenal around, it’s fairly reminiscent of Ryan Pepiot’s fastball last season, with similar movement and release metrics, as shown above. Pepiot’s heater has looked a little different this year but it performed very well for him last season. Obviously, pitch shape similarity void of further context such as command and its place in the overall pitch design isn’t indicative of success on its own, but it’s worth noting. Having something in common with another good pitch is a strong place to start.


The Slider


This pitch has only changed slightly in the time since Mize was last active in the big leagues. He’s throwing it with the same velocity, 86.0 mph, but from a higher release point and with movement closer to a pure bullet slider. It has a bit less horizontal break and similar vertical movement. This was the pitch he found the most success with during his rookie season, and I think the results will likely be about the same as they were then. It’s a power breaking ball with excellent depth, and the lack of horizontal movement should make it harder for opposite-handed hitters to track.

This next bit should be taken with a grain of salt as it’s a small sample, but his ability to locate this pitch seems to be really good. It didn’t get the whiffs he was looking for in his first start of the regular season, but he was finding the edge of the zone on the glove side over and over again. If he can just get them off the zone by a couple of inches and keep them low he should rack up whiffs with it no problem.


The Splitter


What is now Mize’s third pitch was actually the one that was his calling card as a prospect. For good reason too, it’s an excellent pitch. As you might expect, as his fastball changed, his offspeed pitch changed too, but it’s as great as it’s ever been. As his arm slot seems to be higher now, the pitch is spinning on a higher axis, and as such has lost some depth. What used to be a vertically neutral pitch now rises 4.3”, but it’s moving more on the whole with an extra 3” of run now up to 14.9” on average.

The higher release point makes up for some of the depth lost with the new IVB on this pitch. It still has more than a foot (13.5”) of vertical separation from his fastball which is elite territory. Now the effectiveness of the pitch comes down to his ability to sell the pitch and locate it. It didn’t do what he wanted it to in his rookie season, it didn’t perform like the untouchable death knell to at-bats it was when he was coming up, but I think he can get it closer to that form with a bit more time. It should be the best thing he has to offer.


The Curveball


Mize’s curveball is fine but uninteresting. He’s been throwing it with a bit of power at 81.1 mph, and he’s used it almost exclusively when he’s been even or ahead in the count. Its movement isn’t terrible, with -13.0” of IVB, and 7.8” of glove side break. It may not get a ton of whiffs compared to other curves but it should at least get some called strikes if he can find the zone with it. It’s worth having in the back pocket, but it’s nothing special.


The Sinker*


This section comes with an asterisk because he hasn’t thrown his sinker at all since coming back. It was the lesser of his two fastballs when he was last healthy, and with the amount of IVB his 4-seam gained via the mechanical change, I doubt it’s gotten better the way that that pitch has. Rising fastballs and sinkers don’t get better in tandem, they generally take away from the other in pursuit of bettering themselves. That’s what makes pitchers capable of throwing both well so rare. I have my doubts that Mize is one of those pitchers. This pitch may be permanently shelved, and of course, there’s no video of him throwing it since he’s come back, so no GIF. I just thought it was worth mentioning as it was a significant part of his arsenal previously.


The Outlook


So the question now becomes: “What’s in the way of Mize becoming the pitcher we all want him to be?” Put simply, fine-tuning. That’s far too broad a statement as it could be made about any pitcher, here are the specifics:

I need him to figure out how to throw his fastball high and keep it out of the middle and lower parts of the zone. He could potentially try the occasional called-strike fastball that catches the low glove-side corner a la Gerrit Cole but that shouldn’t be his main focus with the pitch. This heater is designed to miss bats high in and above the zone. Use it as such.

As mentioned previously, I want to see just a bit more refinement on those slider locations. The feel for locating it is clearly there, just need to slide the target over a bit. It has the potential to be a knockout pitch in platoon matchups, it’s so close to being that.

His splitter is probably the best pitch he throws from a stuff perspective. His command of it in the past has been a bit spotty, so sharpening that has to be a focus. It doesn’t need to be perfect, a pitch this nasty can miss bats as long as it’s thrown well enough to entice a swing in the first place.

He did well against right-handed hitters in his rookie season despite having an arsenal much better suited for beating lefties. I don’t know if he’ll be able to maintain that again this season with no sinker. If the sinker is gone for good, there needs to be something else, something he can turn to to stump same-handed hitters. Sweepers come with the inherent risk of messing up his ability to throw his other stuff properly but if righties become an issue it might be worth a shot.

It probably wouldn’t be the most unique or fantastic sweeper given Mize’s lack of aptitude for high-spin pitches, and the lack of speed on his curveball. That said you can teach a sweeper to almost any pitcher, there are different grips for different pitchers. He’s probably capable of something in the low 80s with enough break to get past the bats of righties should the need arise.

Enough hypotheticals, let’s talk about now. Mize is likely going to come with his fair share of frustrations this year. This is a guy who’s pitching in competitive games for the first time in almost two years, due to rehabbing from elbow surgery. It takes time to shake off the rust. He will also likely need a bit of time to adjust to how his arsenal has changed since then. While his current pitches are in the same spirit as his old ones, they move a bit differently and he releases them differently. It’s all part of the process.

I’m rooting for it to click for him right away. I’d love to see the best version of Casey Mize right out of the gates. The reality may be a bit rockier than that. What I ask is that you be patient with him. He’s so close to being great. As much as everyone who believes in him wants to be proven right, there’s no doubt in my mind he wants it more. You don’t make these changes unless you want it badly. And if the guy with the talent and work ethic to reach the level of hype that he did is itching to make good on it, I have every reason to believe that he will.

Jack Foley

Jack is a contributor at Pitcher List who enjoys newfangled baseball numbers, coffee, and watching dogs walk by from the window where he works. He has spent far too much time on the nickname page of Baseball-Reference.

2 responses to “The Case For Casey Mize”

  1. Anon says:

    He didn’t overwhelm today with only 7 swings/misses and a 20% CSW, and a few too many hard hit balls but he averaged 96.7 mph and touched 98.4.

  2. Donk says:

    Big missed opportunity not titling this “The Casey for Mize”. Otherwise great write-up!

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