Seattle Mariners’ Kirby to start ALDS Game 1; Castillo gets Game 2

George Kirby will get the ball when the Seattle Mariners open the 2025 playoffs with Game 1 of the ALDS on Saturday.

Oct 3, 2025, 1:54 PM Updated: 11:14 pm

Seattle Mariners George Kirby ALDS Game 1 starter...

SEATTLE, WASHINGTON - SEPTEMBER 23: George Kirby #68 of the Seattle Mariners looks on before the game against the Colorado Rockies at T-Mobile Park on September 23, 2025 in Seattle, Washington. (Photo by Steph Chambers/Getty Images)

(Photo by Steph Chambers/Getty Images)

The Seattle Mariners are going with George Kirby as their starting pitcher in Game 1 of the American League Division Series against the Detroit Tigers on Saturday night.

Luis Castillo will get the ball for Game 2 on Sunday night.

“We feel like our entire starting staff is so solid, and we’re excited to send those two guys out the first two games,” Mariners manager Dan Wilson said after announcing his first two starters during a press conference Friday afternoon. “… We’ve got four guys that we’re going to be able to run out in this series that are going to give us outstanding outings, and we feel good about that.”

The ALDS is set: Seattle Mariners will face Detroit Tigers

Kirby and Castillo both delivered gems during Seattle’s most recent playoff run back in 2022.

Kirby threw seven shutout innings in the Mariners’ 1-0, 18-inning loss to the Houston Astros in Game 3 of the ALDS, which was the franchise’s first home playoff game since 2001. Castillo spun 7 1/3 scoreless innings in Game 1 of Seattle’s AL Wild Card Series sweep in Toronto, then added seven innings of three-run ball in Game 2 of the ALDS in Houston.

“I was super honored,” Kirby said of starting Game 1. “It’s a big game and something you always dream of, being able to start Game 1 or any game in the playoffs, for that matter.”

Lock it in 🔒

George Kirby is your ALDS Game 1 starter, while Luis Castillo gets the nod in Game 2. #SeizeTheMoment pic.twitter.com/U8NCjDmIzR

— Seattle Mariners (@Mariners) October 3, 2025

With 2025 All-Star Bryan Woo still working back from a pectoral issue, it likely came down to some combination of Kirby, Castillo or Logan Gilbert to start the first two games of the series.

Mariners RHP Bryan Woo’s status for ALDS remains unclear

Wilson said the Mariners weighed a variety of factors when making their decision. Among those factors, he acknowledged, were some of the dramatic home-road splits.

As a whole, Seattle’s rotation is considerably better inside pitcher-friendly T-Mobile Park than on the road. But Kirby has had the biggest struggles away from home, sporting a 5.16 road ERA. Kirby’s home ERA is 3.38.

By pitching Kirby in Game 1, the Mariners would avoid using him on the road in Game 3 or a potential Game 4.

“Some of those factors play hard,” Wilson said. “Some of them don’t. And we’ve tried to take it all in. … Starting pitching is one of our strengths, and we trust anybody that goes out there to give us a solid outing.”

The 27-year-old Kirby went 10-8 with a 4.21 ERA and 1.19 WHIP in 23 starts (126 innings) this season. He missed nearly two months at the beginning of the season due to right shoulder inflammation.

Kirby was an All-Star in 2023 and had MLB’s lowest walks per nine innings and best strikeout-to-walk ratio in each of 2023 and 2024.

Over Kirby’s final three starts of the season, he allowed just four earned runs on 11 hits and one walk over 17 1/3 innings.

“We saw some really good outings from George late in the season,” Wilson said. “(And) as we talked about, his ability to attack the strike zone. I think we saw something in George especially – all our guys, really – kind of find that mental spot and that mental space to go to and really compete.

“And George was able to do that down the stretch. And his ability to attack, his ability to put guys away – he’s had some big outings for us during our streak there toward the end, and it’s just a good spot for him to go out there again and continue that same mode that he’s been in.”

A three-time All-Star, Castillo posted a 3.54 ERA in 32 outings with 162 strikeouts and 46 walks across 180 2/3 innings in this year. He was the only pitcher in Seattle’s rotation who didn’t miss a start this season.

The 32-year-old Castillo had a rocky August, but he closed strong with a 1.07 ERA over his final four starts. He went at least six innings and allowed one run or fewer in each of his final four outings.

Gilbert seems likely to start Game 3 in Detroit, but Wilson wasn’t ready to announce the team’s plans beyond the first two games.

Wilson also was noncommittal when asked if Woo will be on the ALDS roster. He said it depends how Woo’s arm responds after going through a throwing session off the T-Mobile Park mound on Thursday.

“We’re going to continue to see how he feels today when he gets here for the workout,” Wilson said. “And again, we’ll continue to gather that information from him and his health, and we’re going to make those decisions later today and in terms of the roster as well.”

Game 1 of the ALDS is set for a 5:38 p.m. Saturday first pitch at T-Mobile Park, while Game 2 will begin at 5:03 p.m. Sunday.

Click here for details on Mariners Radio Network coverage of the ALDS from Seattle Sports.