Logan Gilbert is Taking Off
A closer look at the progression of Gilbert’s pitch arsenal.
The following article is adapted from a piece that was originally intended to be published on Pitcher List; however, I decided to publish a different article instead. To read more of my work that is published at Pitcher List, click on the attached hyperlink.
Most of the discussion regarding who has been the best pitcher in Major League Baseball this season has, deservedly so, been surrounding the outstanding performances of Tarik Skubal and Paul Skenes. Skubal has been utterly dominant in 2025, with a 30.5% K-BB over 140.2 innings pitched, and Skenes is currently posting a 1.94 ERA over 144.0 innings pitched. While the performances of Skubal and Skenes are truly in a league of their own, I believe a player who belongs in the same conversation is Logan Gilbert of the Seattle Mariners.
While Gilbert has pitched fewer innings than Skubal and Skenes due to a right flexor strain that caused him to miss all of May, Gilbert’s peripherals indicate that he’s been dominant when he’s on the mound, producing a 28.9% K-BB over his first 83.1 innings pitched of the season. With a pitch arsenal headlined by a plus slider and splitter, Gilbert’s willingness to tinker with his pitch mix and experiment with different pitch shapes has played a major role in his excellent start to the 2025 season. This article will discuss the changes Gilbert has made to his pitch arsenal throughout his career, break down his dominant start to 2025, and attempt to identify whether he will be able to maintain this level of success throughout the remainder of the season.
Over the past three seasons, Gilbert has arguably been the best starting pitcher in the Seattle Mariners’ excellent starting rotation, displaying a valuable combination of durability and on-field production, pitching in at least 190 innings and possessing an above-average K-BB% in each of the past two seasons. This has resulted in Gilbert producing 3.1 fWAR in 2023 and 4.1 fWAR in 2024. While the aforementioned right elbow flexor strain has eaten into Gilbert’s innings total this season, he has been able to improve his strikeout rate while maintaining his low walk rate, currently producing a 35.1% strikeout rate and 6.3% walk rate over his first 83.1 innings pitched of the season. While Gilbert’s ERA suggests that he performed slightly better last season, his SIERA has improved from 3.19 in 2024 to 2.55 in 2025, indicating that he has been “unlucky” in terms of his on-field performance.
Gilbert has been utterly dominant against both right and left-handed hitters to begin the 2025 season. As shown by the table above, Gilbert is currently producing a 37.6% strikeout rate, 5.8% walk rate, and 31.8% K-BB against right-handed hitters, while producing a 32.5% strikeout rate, 6.7% walk rate, and 25.5% K-BB against left-handed hitters
Why has Gilbert been able to experience such success against both right and left-handed hitters? It is because he possesses a platoon-neutral arsenal, which includes pitches that he can effectively utilize to hitters of both handedness. As shown by the movement plot above, Gilbert’s pitch arsenal contains five pitches: a four-seam fastball, a slider, a splitter, a curveball, and a sinker. Gilbert uses all five pitches to both right and left-handed hitters, particularly toggling down the usage of his curveball when facing hitters of the opposite handedness (11.9% usage vs. RHH, 3.6% usage vs. LHH). Gilbert’s most commonly used breaking ball has been his slider, with the offering’s combination of stuff and location quality (107 aStuff+, 107 aLocation+) allowing for the pitch to be arguably the best in Gilbert’s arsenal (110 aPitching+).
With two strikes, Gilbert toggles up the usage of his splitter considerably, utilizing the offering 40.3% of the time to right-handed hitters and 42.2% of the time to left-handed hitters in two-strike counts this season. Gilbert’s splitter is the most effective swing-and-miss pitch in his arsenal, with the offering generating a 50.6% whiff rate in 2024 and a 51.9% whiff rate so far this season. Gilbert can kill a lot of spin on the baseball when utilizing the splitter, with the offering averaging 749 RPM, and the pitch has also been effective at generating sub-optimal contact, with opposing hitters currently producing a .113 xwOBA against the offering. While only thrown 25 times early in the count to left-handed hitters, the offering has been extremely effective as a “surprise pitch” in this count state, generating a 90.9% (!) whiff rate.
Besides these two dominant pitches, Gilbert also utilizes a four-seam fastball, curveball, and sinker, which he uses in all count states against both-handed hitters. While his fastball, curveball, and sinker offer additional looks to keep hitters honest, it’s the transformation of Gilbert’s slider that has served as the most impactful tweak to his arsenal in recent years.
Upon making his Major League debut in 2021, Gilbert displayed a slider that was closer to a sweeper in shape than his current gyro slider. In 2021, Gilbert’s slider averaged 83.5 MPH, with 4.2 inches of induced vertical break and 6.4 inches of horizontal break. In 2022, the slider maintained the same shape; however, Gilbert added a few ticks of velocity to the offering, resulting in the pitch averaging 86.9 MPH. In 2023, Gilbert began throwing the slider shape he still utilizes today, a true bullet slider, that averages 88.7 MPH, 0.3 inches of induced vertical break, and 0.8 inches of horizontal break.
Why did Gilbert make this change to the shape of his slider? It appears that he switched to a bullet/gyro shape to make the pitch more platoon-neutral, allowing him to utilize the pitch more often to left-handed hitters. Sliders with more horizontal break (and sweepers) run larger platoon splits than sliders with tighter movement profiles since the large “sweeping” action of the pitch is easier to identify by hitters when the pitch is moving towards them. Since gyro/bullet sliders are perceived as moving straight downward by the opposing hitter, this allows for the pitch to be effective against both right and left-handed hitters. With the pitch possessing a shape more conductive for utilization against left-handed hitters, Gilbert increased the usage rate of his slider against opposite-handed hitters from 13.8% in 2022 to 25.1% in 2023, with the pitch’s whiff rate against left-handed hitters increasing from 29.2% to 35.9%, and the ground ball rate against left-handed hitters increasing from 43.2% to 58.7%. Gilbert has continued to increase the usage rate of this offering to left-handed hitters in subsequent seasons (with a 37.5% usage rate so far in 2025), and the pitch has turned into an effective platoon-neutral offering in Gilbert’s arsenal.
Another notable change that Gilbert has made to his pitch arsenal throughout his Major League career is that he replaced his changeup with a splitter. Upon making his debut in 2021, Gilbert displayed a more traditional changeup shape, averaging 79.9 MPH, with 5.3 inches of induced vertical break and 14.3 inches of arm-side movement. In 2023, Gilbert replaced this shape with a splitter, with the pitch approaching the "zero line" of induced vertical break in each of the past two seasons. While changeups generally fade away from opposite-handed hitters, splitters drop vertically, resulting in more swing-and-miss as hitters swing over the offering. Splitters and changeups with "drop" (such as a kick change) are typically more effective to utilize against same-handed hitters, as the pitch is "dropping" rather than moving towards them, and after rarely using his original changeup to right-handed hitters in 2021 and 2022, Gilbert is currently utilizing the splitter nearly 20% of the time against righties so far this season. It appears that Gilbert has continuously tweaked the grip he utilizes to throw this pitch, as the average velocity of the splitter has declined from 85.6 MPH in 2023 to 82.3 MPH in 2025, however, despite the declining velocity, the unique shape of the offering has allowed it to baffle both right and left-handed hitters, with the pitch currently generating a 51.9% whiff rate against a .113 xwOBA.
Both pitchers throw from different arm angles and have different average velocities, so it is not a perfect comparison, but Gilbert's splitter reminds me of Roki Sasaki's splitter. Both pitchers are able to suppress spin on the offering (with Gilbert's splitter averaging 749 RPM, and Sasaki's averaging 483 RPM), and both pitchers have similar movement profiles on their splitters. The main difference between these pitchers’ splitters is that Gilbert has displayed a solid ability to command his splitter, compared to Sasaki, who has run into command issues throughout his brief Major League career. Splitters can be difficult to command due to the complexity of the pitch's grip, leading to an inconsistent movement profile, which allows for the pitch to be both difficult for hitters to square up and for pitchers to command. Gilbert's ability to consistently locate this pitch at the bottom of the zone has allowed for the splitter to generate high whiff rates over the past two seasons, and to be an effective putout pitch when Gilbert utilizes the offering with two strikes.
The progression of Logan Gilbert’s pitch arsenal from the beginning of his Major League career to the present day is a story regarding the importance of a pitcher possessing the ability to tinker with their arsenal and displaying the ability to make the necessary adjustments to their pitches to more effectively face opposing hitters. Tightening his slider shape has allowed Gilbert to more effectively utilize the offering against both right and left-handed hitters, while his splitter has developed into one of the best off-speed pitches in all of Major League Baseball. In 2024, Gilbert added a cutter to his arsenal; however, he has largely removed it from his repertoire so far in 2025. Should Gilbert experience trouble against left-handed hitters over the remainder of the season, I would expect Gilbert to re-introduce this pitch to his pitch mix, providing him with an additional fastball he can utilize against hitters of the opposite handedness. As Gilbert continues refining his approach, his ability to adapt and iterate on his arsenal gives him a strong foundation to remain among the league’s most effective starters, and if he sustains this stuff and location quality over the remainder of the season, then a peak season from Logan Gilbert may already be underway.
Thanks for reading!
Follow @MLBDailyStats_ on X and Adam Salorio on Substack for more in-depth MLB analysis. Photo credits to Kirby Lee.
Statistics as of the end of play on August 7th, 2025.