Mariners activate George Kirby for season debut

The Mariners announced Thursday that right-hander George Kirby has been reinstated from the injured list. He’ll make his 2025 debut today against the Astros. Righty Troy Taylor was optioned to Triple-A Tacoma last night to open a spot on the roster for Kirby’s return.

The first-place Mariners have surged to a 28-20 record this season despite not getting a single pitch from arguably their best starter. The 27-year-old Kirby has been out all season after the Mariners opted for a cautious approach when Kirby was diagnosed with shoulder inflammation during spring training.

A first-round pick back in 2019 (No. 20 overall), Kirby quickly became one of the Mariners’ top pitching prospects and was soon regarded as one of the top prospects in the entire sport. He breezed through the minors and could very well have debuted even sooner were it not for the canceled 2020 minor league season.

Kirby broke through to the majors in 2022 and hasn’t looked back. He pitched 130 innings over the life of 26 starts in his rookie season and turned in a 3.39 ERA with a 24.5% strikeout rate and 4.1% walk rate. Few pitchers can sustain a walk rate that low, but Kirby has actually improved upon that mark in subsequent seasons. He was touted as having the best command of perhaps any top pitching prospect in the sport prior to his debut, and he now has a legitimate claim to the best command of any pitcher in Major League Baseball.

Since his 2022 debut, no starting pitcher has a lower walk rate than Kirby’s 3.1% mark. Only one qualified reliever in that time has a better walk rate (Chris Martin, at 2.8%). You’d have to drop the threshold to a minimum of 20 innings pitched (total) since 2022 to find a second pitcher with a lower walk rate than Kirby.

Kirby’s pinpoint command is all the more deadly when one considers that he’s not the archetypal soft-tossing, finesse pitcher typically associated with this type of precision. He’s averaged 95.8 mph on his four-seamer in his career and sat 96.1 mph with the pitch from 2023-24.

Kirby was an All-Star in 2023 and finished sixth in AL Cy Young voting that season. He’s started 89 big league games for the Mariners since his debut and touts a 3.43 ERA, 23.3% strikeout rate and 43.4% ground-ball rate to go along with that pristine walk rate. Those strikeout and grounder rates are only a bit better than average, but a pitcher who averages less than a walk per start doesn’t need to pile up strikeouts or ground-balls at league-leading rates to be among the most effective pitchers in the sport.

The Mariners are getting Kirby back at an ideal time. Rotation-mates Logan Gilbert (flexor strain) and Bryce Miller (elbow inflammation) are both on the 15-day injured list at the moment. Seattle is also set to square off against the second-place Astros for a four-game series. Houston has been a league-average team against right-handed pitching this season, and the ’Stros are currently without their top left-handed bat: designated hitter Yordan Alvarez (though he has uncharacteristically struggled versus righties this season). The only left-handed hitters on Houston’s roster are switch-hitting catcher Victor Caratini and backup catcher Cesar Salazar. Kirby held right-handed hitters to an awful .234/.257/.360 slash in 2024.