Seattle’s George Kirby Commands His Repertoire

George Kirby
Jerome Miron-USA TODAY Sports

George Kirby is off to a solid start in Seattle. Since debuting with the Mariners in early May, the 24-year-old rookie right-hander has a 4.04 ERA and a 4.73 FIP (numbers that were markedly better before last night’s career-worst outing) to go with 49 strikeouts in 53 innings. Lending credence to scouting reports — our Eric Longenhagen lauded not only his high-octane heater, but also his plus-plus control — Kirby has issued just seven free passes.

Drafted 20th overall in 2019 out of Elon University, Kirby ranked No. 3 on our 2022 Seattle Mariners top prospects list. Kirby discussed his early career development, including what he’s learned from analytics, earlier this month.


David Laurila: You’ve had access to a ton of information playing in the Mariners’ system. What are some of the ways you approach pitching differently than you did just a few years ago?

George Kirby: “One thing I’ve really tried to hammer on is being location-based. I look at the analytics for certain pitches. With my slider, for instance, there is my release point and the horizontal movement. There are good tools to see where you’re at and kind of how to manage your off-speed. I’m always looking at that stuff.”

Laurila: By location-based, I assume you’re referring to how your pitches play best in certain zones?

Kirby: “Yes. With the Mariners, we have our ‘green clouds,’ which show the best pitch in that location in certain counts. I try to really focus on that. And one of the biggest numbers is that 94% of the time when you throw a first-pitch strike, you’re either getting the ball back 0–1 or it’s an out. That’s a huge part of pitching — not being scared of the zone and allowing that first pitch to work in your favor.”

Laurila: These are things you’ve learned since getting to pro ball.

Kirby: “Yes, ever since I’ve been with the Mariners. You get your pitch grades and, like I was saying, they tell you what works best in certain counts and certain locations. That stuff is really important.”

Laurila: Which of your pitches grades out the best analytically?

Kirby: “My changeup, usually. Best action. The process score of it.”

Laurila: Is that something you would have anticipated, that your changeup would grade out the best?

Kirby: “I always thought so. It’s a pitch that I’ve been able to locate pretty well, and the movement profile has been pretty darn good. It’s more horizontal. I like to be between 14 and 18 inches horizontal to arm-side. Sometimes, if I want to use it middle-down, I’ll try to focus on ripping it down. In some situations, vertical movement might play better that horizontal movement.”

Laurila: Is horizontal movement natural for you?

Kirby: “Yeah, just kind of the way I grip it and have it come off my fingertips. The little pronating I do allows me to create the full horizontal spin I’m looking for. I throw it with a four-seam grip, kind of a half circle, and try to press my fingertips above the seam. That way I know I’m not choking it.”

Laurila: Where did you learn your changeup?

Kirby: “In high school, from my pitching coach. It was something that felt really natural to me with my arm slot. It’s just always been a great pitch for me.”

Laurila: What about your breaking balls?

Kirby: “I’ve thrown my curveball the same way since Little League. I spike it, and usually when it’s really good it’s more vertical. I’ve seen it be 15 to 18 vertical and usually eight to 12 horizontal. I kind of get the best of both worlds there. And when I’m throwing it the best, I’m throwing it with high intent. [Velocity-wise] it’s somewhere around 80 to 83 [mph].”

Laurila: You throw a slider as well.

Kirby: “I do. I’ve started throwing it harder, just because it feels a little more natural with my arm slot, instead of trying to sweep it.”

Laurila: And your fastball is a four-seamer.

Kirby: “Yes. I get some ride on it. My fastball plays really well on the top of the zone. If I can focus on riding it up there, I’ve got a really good chance of getting some swings and misses.”

Laurila: You know where your pitches play best. That said, are you concerned with hitters’ hot zones, or are you primarily attacking with the idea that your best stuff is going to beat anybody?

Kirby: “Most of the time, I’m just attacking. Some guys are definitely better in certain locations, so you have to be able to handle their weak spots, but my thought processes is that I’m better than the hitter. I’m going to come at them with my best stuff and beat them.”

David Laurila grew up in Michigan's Upper Peninsula and now writes about baseball from his home in Cambridge, Mass. He authored the Prospectus Q&A series at Baseball Prospectus from December 2006-May 2011 before being claimed off waivers by FanGraphs. He can be followed on Twitter @DavidLaurilaQA.

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2 months ago

For a guy with good stuff, he doesn’t strike out as many as you’d expect (kind of like Stroman).

Do you think it’s a matter of him still learning, or is there something about his repertoire that is easier for hitters to make contact?

Great interview, by the way.

2 months ago
Reply to  dl80

I wonder if Kirby is a guy who has to start throwing more balls in order to get more Ks. His fastball has enough movement but is not exceptional. He may have to mess with hitter expectations by going outside of the zone a bit more…?

Lunch Anglemember
2 months ago
Reply to  dl80

He throws a lot of pitches in the zone, and he throws a lot of fastballs. Kirby’s fastball is great, but it’s not a Rodon fastball or anything. He’d strike out more batters if he threw more secondary pitches and if he went out of the zone trying to get more chases, but that doesn’t seem to be his style.

Striking out even 21% of batters is impressive when you only walk 3%!

2 months ago
Reply to  dl80

Kirby’s approach is similar to Logan Gilbert’s approach last year. Establish the fastball, flood the zone, and then work the other stuff in later. I wonder if it’s part of Seattle’s plan for their young starters to get their feet wet.