Since making his Major League debut with the Seattle Mariners in 2022, starting pitcher George Kirby has shown exceptional talent. Known for his rare ability to combine fastball velocity reaching the upper 90s with pinpoint control, Kirby draws early comparisons to Hall of Famer Greg Maddux. His pitching development has been a focal point for the Mariners as they anticipate his continued growth.
Kirby’s early career achievements include finishing sixth in the 2022 Rookie of the Year voting despite a late-season start and earning All-Star honors in 2023. Across his first three seasons, Kirby consistently maintained an earned run average (ERA) below 3.53 and kept his walk rate under 4.1%. However, he faced setbacks in 2025 after missing the first two months of the season due to right shoulder inflammation, marking his first stint on the injured list.
Potential for Improvement in 2026
With a challenging 2025 behind him, Kirby is positioned as a leading candidate for a strong rebound in the upcoming season. Analysts and Mariners insiders believe there is untapped potential waiting to be unlocked, particularly in refining his secondary pitches to complement his fastballs effectively.
During a recent Seattle Sports broadcast, both co-host Stacy Rost and Yahoo Sports’ Jordan Shusterman shared insights on what could help Kirby elevate his game. Shusterman highlighted the uncertainty surrounding which secondary pitch might become Kirby’s go-to strikeout weapon, a question that remains central to his pitching development.
Secondary Pitches and Strikeout Capabilities
Shusterman explained the significance of a successful secondary pitch by referencing pitcher Logan Gilbert, who developed a splitter that significantly increased his swing-and-miss rate. He suggested that Kirby is still searching for a similar pitch to broaden his effectiveness beyond his strong fastball arsenal.
“I think with him what’s always interesting, and this is true for really all of these pitchers but especially with him and Logan (Gilbert) and Bryce (Miller), just the number of pitches that they throw. You really don’t know exactly what is the secondary pitch that is going to help him get to the next level,” Jordan Shusterman, Analyst at Yahoo Sports
“I think Logan Gilbert clearly figured that out with his splitter. That unlocked the level of swing and miss that he wasn’t getting earlier in his career, and that’s something that Kirby I think is still looking for.” Jordan Shusterman, Analyst at Yahoo Sports
In 2025, Kirby recorded the highest whiff rate of his career at 26.7%, placing him in the 61st percentile among qualified pitchers and marking the first time his whiff rate surpassed the league average. Despite this improvement, his secondary offerings have yet to become definitive strikeout tools. Kirby earned most of his strikeouts on his four-seam fastball (51) and added 26 more on his sinker, with his slider contributing 33 strikeouts, the highest total on any non-fastball pitch.
Finding the Key Secondary Pitch
Shusterman suggested that Kirby’s next breakthrough could stem from developing a more effective secondary pitch, possibly a splitter or another breaking ball. He emphasized that Kirby’s strong command sets a solid foundation for expanding his repertoire.
“Maybe it is a splitter, maybe it’s another breaking ball. We know he’s capable of adding a lot of pitches, but the command is always going to be there,” Jordan Shusterman, Analyst at Yahoo Sports
“… As it has been with Kirby for a while, it’s just about finding the secondary pitch where you can get more swing and miss.” Jordan Shusterman, Analyst at Yahoo Sports
Implications for the Mariners’ Season
Kirby’s continued development is crucial as the Mariners prepare for the 2026 campaign, especially with the upcoming World Baseball Classic influencing spring training plans. Strengthening Kirby’s pitch mix could significantly bolster Seattle’s starting rotation and contribute to the team’s overall success. Alongside other emerging Mariners players like Logan Gilbert, Bryce Miller, and new acquisition Josh Simpson, Kirby remains a key figure in the organization’s pitching future.
As Kirby seeks to build on his promising career while overcoming past injuries, the Mariners and their fans will be watching closely to see if he can unlock that next level of pitching excellence in the coming season.
