George Kirby's long-awaited return will mark a fresh start for struggling rotation

The Seattle Mariners will get a huge piece back in their starting rotation on Thursday, as the team has revealed that ace right-hander George Kirby will make his 2025 debut opposite the Houston Astros.

Bob Condotta of The Seattle Times is among those who broke the news on Wednesday ahead of the Mariners' rubber match against the Chicago White Sox. Kirby will face Lance McCullers Jr., who only just returned from a long injury absence in his own right, in the opener of a four-game set in Houston.

More than two months have passed since Kirby first went to the sidelines with inflammation in his right shoulder. It always figured to be a challenge for Seattle's rotation to overcome his absence, but nobody could have anticipated just how bumpy the road would be.

Basically everything has gone wrong for the Mariners rotation while Kirby has been recovering from his shoulder injury

After leading all of MLB with a 3.38 ERA in 2024, Mariners starters have seen their ERA jump up to 3.76 thus far in 2025. Even the distance between those two figures doesn't tell the whole story, as it notably obscures how much of a toll injuries have taken.

After Miller, Logan Gilbert (flexor strain) and Bryce Miller (elbow inflammation) also eventually landed on the IL, effectively nixing 60 percent of the starting five that carried the Mariners to 85 wins last season. Bryan Woo and Luis Castillo have done their best to pick up the slack, but fill-ins like Emerson Hancock and Logan Evans have been inconsistent.

Yet with the Mariners getting consistent good news on Gilbert and Miller, Kirby's return on Thursday has the potential to turn the tide for good when it comes to Seattle's rotation. Provided, of course, that he's the same pitcher he was in his first three seasons with the Mariners.

This is technically a "we'll see" scenario, but Kirby sure looked like himself in three rehab starts for Triple-A Tacoma. His fastball got as high as 97.8 mph, and he fanned 13 batters while walking only two in 10 innings.

Just as a reminder, the last two seasons saw Kirby post a 3.44 ERA over 381.2 innings while leading the majors in strikeout-to-walk ratio both years. He's a No. 1 on most of the staffs around the league.

If everyone is fully healthy, though, he's the Mariners' No. 2 behind Gilbert and arguably even their No. 3 behind the increasingly dominant Woo. This is a notion that should certainly excite Mariners fans, while otherwise frightening those of the competition in the AL West.

After all, even despite Kirby's long absence and the more recent ones of Gilbert and Miller, the Mariners are already 27-20 and in first place in the division. If the tide does indeed turn on Thursday, there may be no catching the Mariners after that.