Mariners ace George Kirby has exciting new pitch to unlock further dominance

George Kirby is already one of the best pitchers in MLB at limiting walks, and for at least one obvious reason.

He heavily relies on his four-seam fastball, allowing him to attack hitters and avoid free passes. He has depended on that four-seamer especially with two strikes, throwing it approximately 40 percent of the time in such situations. Yet while his fastball is impressive, this reliance may have limited his success against lefties.

One storyline that has dominated spring training is Mariners pitchers learning new pitches. Andrés Muñoz could become even more dominant (is that even possible?) by finding a solid changeup. Logan Gilbert and Bryce Miller are always tinkering with new pitches, but it is Kirby who has sort of flown under the radar by adding a cutter, as covered by Eno Sarris of The Athletic.

By introducing a cutter, Kirby is looking to diversify his pitch selection, making it more difficult for hitters to anticipate and connect.​

George Kirby shows off cutter during spring training, following in Logan Gilbert and Bryce Miller footsteps

Kirby's decision to develop a cutter is influenced by the success of his teammates, Gilbert and Miller, who have both expanded their arsenals with new pitches. Gilbert, for instance, added a split-finger fastball in 2023 and later incorporated a cutter in 2024, leading to various career highs and establishing himself as arguably the Mariners best pitcher. Similarly, Miller debuted a new cutter during spring training, showcasing his commitment to evolving as a pitcher. 

Kirby's cutter is expected to mirror Miller's, providing a pitch that moves differently than his fastball and slider, hopefully keeping hitters off balance.

Something we saw all too often in 2024 was Kirby looking to get ahead of hitters and them being aggressive on his fastball, resulting in early damage. His cutter at least offers a different look.

It could also be beneficial in reducing his platoon split against left-handed batters, who had a 109-point OPS advantage relative to right-handed hitters in 2024. By offering a pitch that can jam lefties with movement toward the handle, Kirby can induce weaker contact or increase strikeouts.​

Given Kirby's already impressive command and control, the addition of a cutter could elevate his game to new heights. Some projections even suggest that with this enhancement, Kirby could emerge as a contender for the Cy Young Award, thus following Gilbert's example after he finished sixth in the 2024 AL Cy Young voting.

As fans eagerly anticipate how this new development will unfold in the upcoming season, Kirby's commitment to refining his craft exemplifies the Mariners' culture of analytics and always striving for improvement and innovation. With a more versatile pitching arsenal, Kirby could be poised to take that next step into the more elite category.