Know Your Averages, Splitter Edition

The splitter’s usage among starting pitchers reached a 14-year high in the 2024 season when it hit a 3.2% usage league-wide. In the past four seasons, no qualified pitcher has taken the top splitter usage trophy away from Kevin Gausman who averaged around 36% usage from 2021 to 2024. Taijuan Walker came close in 2023 when he threw his splitter 33.2% of the time, yet it wasn’t enough to top the king. 2025 seems like the year in which Gausman will lose his crown. Roki Sasaki will be one of the most-watched pitchers in 2025 and according to some, will showcase one of the best splitters in the world. How often he’ll use that pitch remains to be seen. Shota Imanaga (30.6% usage) came close to King Gausman’s mark in 2024. In Yoshinobu Yamamoto’s 90 innings pitched in 2024, he threw his splitter 24.2% of the time. What will happen in 2025? Dare I suggest the league-wide splitter usage continues its growth and finishes at 4.1%? It’s possible. Only 12 qualified pitchers threw splitters in 2024. In this edition of “Know Your Averages”, I’ll bring in any pitcher who threw at least 45 splitters and compare their plate discipline metrics.

Fastballs: Four-seamers | Sinkers | Cutters

Breaking and Offspeed Pitches: Sliders | Changeups | Curveballs | Splitters | Sweepers

My process relies on Alex Chamberlain’s Pitch Leaderboard which utilizes Statcast data that you can also find at Baseball Savant and our (New!) Pitch Type Splits on player pages. Here is a quick look at how the splitter stacks up against other offspeed and breaking balls in several measurements:

Let’s look at the pitchers below, at, and above average with their splitters in each measurement. A lot of what follows in the “Questions or comments?” section is less analysis and more points for further research or discussion.

NOTE: The chart and table above do not include a minimum pitch qualifier. The players in the analysis below will fall under a 45-pitch minimum qualifier with some arbitrary author finagling.

—Zone%—

• Tyler Mahle – 63.8%
• Zack Littell – 38.1%
• Tylor Megill – 23.5%

Questions or comments?: Was Mahle successful by throwing his splitter in the zone so often in 2024? Not really. It was hit for a .392 wOBA. Its SwStr% was below average and it returned a negative run value. Still, it forced ground balls 66.7% of the time and the pitch did not give up an extra-base hit. On the opposite end of the spectrum, Tylor Megill’s newly found 2024 splitter was chased outside of the zone 37.5% of the time, well above average. Thanks to all that chase, his splitter ended up with an above-average SwStr% (21.0%), but earned negative run value thanks to a few mistakes that ended as home runs.

—Swing%—

• Shota Imanaga – 63.3%
• Yu Darvish – 51.4%
• Hunter Greene – 41.1%

Questions or comments?: Imanaga threw the splitter 30.6% of the time in 2024, good for third among qualified pitchers. It was swung on often, but it was also swung on and missed often with a 26.2% SwStr%. By pVal the pitch returned an 11.0! The pitch was chased often (47.5% O-Swing%), seldom connected with when in the zone (70.6% Z-Contact%), and was only hit for a .219 wOBA. George Kirby (51.7%) should be mentioned as a starting pitcher who gets average swing rates on his splitter along with Yu Darvish. Hunter Greene’s splitter was his third worst by wOBA, third worst by SwStr%, and swung on so rarely because of its below-average 37.9% Zone%. Furthermore, hitters simply did not chase it out of the zone often enough. Could it be brought in the zone more often? That might not be good advice as when it was in the zone, it was connected with at a high 89.7% of the time.

—SwStr%—

• Fernando Cruz – 32.6%
• Colin Rea – 15.3%
• Chris Bassitt – 7.8%

Questions or comments?: Remember that Paul Skenes returned a 30.6% SwStr% on his changeup, over two times the average. Cruz is beating that mark with his splitter and more than doubling the average. Cruz threw 477 splitters in 2024 and not a single one of them went out of the park. Hitters put the splitter on the ground (GB% 51.5%) more than half the time and when the pitch was in the zone, it was connected with (Z-Contact%) only 64.2% of the time. It was thrown in the zone less often than average and chased more often than average, but it was all over the zone in total. Hitters likely had a difficult time recognizing the pitch from his four-seamer while they were really hoping to hit one of his poor fastballs (Cutter: 81 Stuff, .504 wOBA, Four-seamer: 84 Stuff+, .374 wOBA). Maybe the Yankees can develop his fastball?

—CallStr%—

• Tyler Mahle – 24.6%
• Casey Mize – 8.0%
• Yonny Chirinos – 0.0%

Questions or comments?: Yonny Chirinos didn’t get a single called strike?! It did well enough from a wOBA (.234) measure thanks to a high chase rate. Mahle returned so many called strikes because of his very high zone rate, but that combination didn’t stop hitters from doing damage when they did swing.

—CSW%—

• Fernando Cruz – 41.3%
• Bryce Miller – 23.8%
• Yonny Chirinos – 10.5%

Questions or comments?: Cruz again! He was the king of one of the two metrics (CStr% + Whiff%) that combine to create CSW% and he overpowered the combination with swinging strikes. You can see the same type of connection between Chirinos’ low CStr% and his low CSW%. That’s part of the reason he’s moved on to a second phase of his career in Korea.

—Chase%—

• Kevin Gausman – 38.0%
• Zack Littell – 27.7%
• Tyler Mahle – 20.3%

Questions or comments?: Splitters must be chased. It’s kind of like their thing. Gausman’s strategy of placing splitters in the low corners of the zone and just outside of it has kept the pitches’ wOBA marks consistently below and well below the .300 mark. But, in 2024 Gausman’s splitter returned its lowest SwStr% (16.0%) of its entire career. He may still be topping the Chase% group, but 2024’s splitter returned its lowest mark in, 37.2%, since 2017. Should we be concerned? Zack Littell’s conversion to full-time starter in 2024 earned him a very respectable 3.63 ERA (4.34 xERA). His splitter and slider were above-average pitches by Stuff+, but neither of his fastballs (four-seam/cutter) were.

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Will Roki Sasaki be the king of splitter talks in 2025? My guess would is yes. Fantasy managers need to keep a close eye on Kevin Gausman’s splitter usage and performance in 2025, it’s possible he’ll loose the crown in 2025.