George Kirby started making noise on his control before he ever donned a Mariners major league uniform. He walked 6 guys over 88 innings his final year at Elon, then didn't walk a single hitter in 23 innings in Everett that year after being drafted. Was this a fluke, or a sign of things to come? In 2021 he had an impressive BB rate of just 2.0/9, followed by a 2022 rate of 2.0/9 once again while he was in the minors. I stress this because guys normally struggle with command out of college as they adjust.
Not George Kirby.
In his 2022 debut season, that rate was actually lower than his overall average, as he walked just 1.5/9 in his 130 innings pitched. If he would've qualified, the 24-year-old would've been fifth in BB/9
Then came 2023. George Kirby was remarkable, putting up video game walk rates. Kirby beat the second-place Zach Eflin by 0.32 BB/9. It may not seem like a ton until you realize that the 1.70 BB/9 rate that Logan Gilbert had was actually 4th in baseball. That's how far ahead of the pack Kirby was. To go along with that, he posted a 9.05 K/BB rate. How good is that? Well, it's only the 8th-best mark of all time—no big deal.
STEAMER doesn't see George Kirby doing it again
They've got him at a 1.53 BB/9 rate, higher than his rookie season. That would be walking 14 more people, or more importantly walking 73.68% more hitters than he did in 2023. Is that reasonable to expect? Possibly. After all, what Kirby did last year was historic. It just doesn't happen that often. However, Kirby did issue 21% of his walks in a two-game stretch. Could you argue there is a chance he posts an even lower BB rate at some point?
He walked six people over his first 14 starts and didn't walk a hitter in the month of August. I'm not saying he is going to post a lower rate, cause that would be remarkable. BUT... if Kirby strikes out a guy an inning like he did his rookie year, and posts an 0.85 BB/9 rate, it would be the third greatest K/BB rate of all time. Just saying.
Anyway, STEAMER has him at 1.53, which is perfectly reasonable and would still be on of the better marks in all of baseball. They've got his K rate, HR rate, BB rate, ERA, and FIP all going up a tiny bit, projecting a 3.5 WAR season. That's lower than last year, but still projects a bit higher than Castillo, and would actually slot Kirby in at a T-13th projection for all starting pitchers in WAR.
Here is his projection line, from STEAMER, for 2024.
George Kirby: 12-11, 191 IP, 3.59 ERA, 3.67 FIP, 8.65 K/9, 1.53 BB/9, 1.18 HR/9, 3.5 WAR