Amongst a loaded rotation, George Kirby is set to become Mariners' top arm in 2024

The Mariners might just have the best rotation in baseball, and George Kirby is set to become the best of the talented group in 2024
Los Angeles Dodgers v Seattle Mariners
Los Angeles Dodgers v Seattle Mariners / Alika Jenner/GettyImages
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Earlier this offseason, as a staff, the SoDo Mojo writers ranked current Mariners based on their projections for the 2024 season. Ascending talent George Kirby was ranked third, just behind 2023 AL Cy Young candidate Luis Castillo. However, in 2024, Kirby may become not just the best pitcher on the Mariners, but one of the best in baseball.

The argument can be made that Kirby has the best command in baseball. As a rookie, he allowed just 1.5 BB/9, and he lowered that number to a league-leading 0.9 in 2023. He also has enough stuff that even though hitters know they will be challenged, they are rarely able to punish him, as shown by his .292 BABIP and 1.04 HR/9, which were both top-25 in the MLB.

In 2024, George Kirby Is Set to Become Seattle's Top Arm

Kirby also excels at getting hitters to chase pitches, thus taking advantage of over-aggressive hitters who know he will pound the strike zone. In 2023, he was in the 88th percentile in chase rate, and his splitter (35.7% whiff rate) and fastball (28.0% whiff rate) were strong pitches, although the splitter was rarely thrown (6.1%). His overall K/9 was 8.1, contributing to a league-leading 9.05 SO/W, which is 8th place in the history of baseball.

If Kirby can bring his K/9 back up to the levels of his rookie season (9.21) while maintaining a BB/9 around 1-1.5, he will have even more success in his third season. With Seattle likely being a better team in 2024, his win total should at least stay the same, if not increase, from his 13 last season.

Kirby will face stiff competition from Castillo and Logan Gilbert on his path to becoming the clear-cut ace in Seattle. In a perfect world, Seattle does their best Atlanta Braves impression and all three pitchers are Cy Young candidates. Unfortunately, it is more likely that one player will leap to superstar status while the other two remain very good, but outside of that upper echelon.

In 2024, that player will be George Kirby. He already possesses one of the best pitches in baseball, as his 99-mph fastball generated a run value of 14 per Baseball Savant, the 10th-best 4-seam fastball in the league. It also ranked top-10 for 4-seam value in 2022. Between his dominant fastball, great splitter, and superb control, it is well within the range of outcomes for Kirby to post an ERA around 3.10, with 15 wins and 200 strikeouts. That stat line would not only make him the Mariners' ace but also garner him serious Cy Young consideration.