Mariners' George Kirby Seeks Breakout Season with Secondary Pitch Development

Analysts believe refining his off-speed offerings could elevate Kirby's game to new heights in 2026.

Published on Feb. 25, 2026

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Since making his MLB debut with the Seattle Mariners in 2022, starting pitcher George Kirby has shown immense potential, combining a high-velocity fastball with pinpoint control. However, analysts believe Kirby's continued development hinges on refining his secondary pitches to complement his dominant fastball arsenal and unlock the next level of his game.

Why it matters

Kirby's growth is crucial for the Mariners as they aim to build a strong starting rotation and contend in the AL West. Developing a reliable secondary pitch could significantly boost Kirby's strikeout capabilities and overall effectiveness, making him a more complete pitcher and a key piece of the Mariners' future.

The details

Kirby has maintained a sub-3.53 ERA and walk rate under 4.1% in his first three MLB seasons, but he faced setbacks in 2025 due to a right shoulder injury. Analysts believe Kirby is still searching for a definitive secondary pitch, such as a splitter or another breaking ball, that could become a reliable strikeout weapon and elevate his game. Improving his secondary offerings would complement his strong fastball command and make him a more well-rounded pitcher.

  • Kirby made his MLB debut with the Mariners in 2022.
  • Kirby earned All-Star honors in 2023.
  • Kirby missed the first two months of the 2025 season due to a right shoulder injury.
  • The 2026 MLB season is approaching, with Kirby poised for a potential breakout year.

The players

George Kirby

A starting pitcher for the Seattle Mariners who has shown exceptional talent, combining a high-velocity fastball with pinpoint control, and is seeking to develop a reliable secondary pitch to take his game to the next level.

Logan Gilbert

A Mariners pitcher who has successfully developed a splitter that has significantly increased his swing-and-miss rate, serving as a model for the type of secondary pitch Kirby could benefit from.

Bryce Miller

Another promising Mariners pitcher whose development is being closely watched, along with Kirby and Gilbert, as the team builds its future starting rotation.

Josh Simpson

A new acquisition for the Mariners who will be joining the team's pitching staff and contributing to the overall strength of the starting rotation.

Stacy Rost

A co-host on the Seattle Sports broadcast who provided insights on Kirby's development.

Jordan Shusterman

An analyst at Yahoo Sports who shared his perspectives on Kirby's need to refine his secondary pitches to reach the next level of his career.

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What they’re saying

“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 (Seattle 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 (Seattle Sports)

“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 (Seattle 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 (Seattle Sports)

What’s next

The Mariners and their fans will be closely watching Kirby's progress during spring training and the 2026 season to see if he can unlock the next level of his pitching potential by developing a reliable secondary pitch.

The takeaway

Kirby's continued development and the refinement of his secondary offerings are crucial for the Mariners as they aim to build a strong starting rotation and contend in the AL West. If Kirby can find a complementary pitch to his dominant fastball, he could elevate his game and become a key piece of the Mariners' future success.