While the sweeper was a focus, so was refining the existing parts of his pitch mix.
Mize knew his four-seam fastball had lost carry, which was something he wanted to try and address. He also knew it was the most difficult pitch to alter.
“We literally just flipped the seams on the ball to try to get more induced vertical break,” Kress said. “This is effectively another seam-orientation trick, trying to produce more carry. It was seen last season by Luke Weaver, where the Yankees changed the seam orientation on Luke Weaver’s fastball and made an enormous jump. That was because he had a very weird fastball grip that was out of the ordinary.”
Mize’s fastball gained an inch of vertical movement this season, even with a slight velocity drop. It was not a major change, but more incremental progress.
Mize was also curious about what Kress would say about his splitter.
His signature swing-and-miss pitch coming out of Auburn had not performed as an elite offering in professional baseball.
“I went in there ‘OK, what are going to do about my split?’” Mize recalled asking.
Initially, the recommendation was to throw the pitch with more velocity. But after uneven results, about halfway through the season, Kress suggested another change: and that was to add more cut, more gyroscopic spin to the pitch.
What Kress has learned about the changeup is differentiating its vertical movement from a pitcher’s primary offering is key.
“When you kill the vertical break, it gets further away from the four-seam cloud, or the four-seam movement profile, and that’s the driver of more swings and misses,” Kress said. “In his case, when he’s able to run it down towards the zero line, the zero vertical line, it just plays so well.”
On the surface, his splitter took a step back this year.
The run values on his splitter (-1.96 wFS per 100 pitches) suggest he should be throwing it less often, not more frequently as he has done in 2025, especially later in the season.
But Mize explains why evaluating standalone pitch values can be problematic.
“I give up a homer on the pitch, and that’s going to negatively affect the value, any type of slug, which is what happens sometimes if I leave (the splitter) up in the zone,” Mize said. “But I threw 28 (splitters) in a particular game and I get eight swings and misses on it. The run value went down because of the damage that happened on a home run and double. I understand how they calculate that, but if you look at it and say ‘Oh, your run value is bad you need to scrap that pitch,’ like, I would be worse without that pitch. I need to throw that pitch.”
For instance, while his splitter’s run value decreased – his fastball finished with a slight positive run value for the first time his rookie year in 2020. This speaks to the power of a wider menu of pitch offerings.
“I think the bigger thing might be the fact that we added more pitches … allowing us to not have to rely on throwing as many four-seamers and therefore letting it produce a little bit better,” Kress said.
Mize finished the season with a five-pitch arsenal, throwing no pitch more often than 34% of the time, and his four-seamer, but throwing each pitch at least 12% of the time. He threw only three pitches at a double-digit clip in 2024.
Even though most of Mize’s offerings do not grade out as wipeout offerings – the combination of pitches in an expanded pitch mix raised his entire game.
And 2025 is just one chapter. Mize and Kress are curious to see where his pitch mix is with another offseason of improvement.
Mize’s story is one of iterating.
It’s also one that demonstrates how coaching staffs both inside and outside of affiliated baseball can work together in harmony.
For instance, Mize believes the Tigers enjoy excellent pitching coaches. They also have access to Hawkeye data that those outside affiliated baseball do not enjoy.
“They do a really good job of reviewing Hawkeye data and seeing how I am moving, trying to get ahead of some mechanical stuff that can bleed over from time to time,” Mize said. “We’ve been able to correct some things before they become too bad of trends which has been super beneficial this year. ‘Hey, you are starting to counter rotate too much,’ or, ‘You are flying open.’”
But he also wanted to go outside to hear other opinions on how to optimize his arsenal and where he could improve. The Tigers signed off on his plan.
“Combining all those things is what has allowed me to take a step forward this year,” Mize said.
And this year is just one chapter. Mize’s development story is not complete. It’s a journey that will continue this offseason, with another breakthrough, another performance jump, well within the range of possibility.