Analysis: Not to be confused with the Luis Castillo already in Seattle's big-league rotation, this 30-year-old righty made his MLB debut with the Tigers in 2022 and threw 3.2 shutout frames while striking out four batters across three relief appearances. He then spent the next two seasons in Japan and is now slated to make his first career start in the majors. A strong showing Friday could buy the lesser-known Castillo another turn through the rotation while the Mariners await George Kirby's (shoulder) return from the IL.

Analysis: Diaz made his one appearance for Seattle on Tuesday. He allowed no runs on one hit with a strikeout in 1.1 innings. The southpaw has made the bulk of his appearances for Tacoma as a starter and figured to get a shot at securing a rotation spot in place of the injured George Kirby (shoulder). After just one relief appearance, he will return to Tacoma. In a corresponding move, Luis F. Castillo is expected to be promoted from Triple-A Tacoma to make his first career start Friday.

Analysis: After taking two days to welcome a new addition to his family, Polanco will officially be back in action for the Mariners' series opener against San Francisco on Friday. The 31-year-old has gone 6-for-15 with four RBI in four games this season and has collected a base hit in each one of them. Leo Rivas was optioned to Triple-A Tacoma in a corresponding move.

Analysis: Rivas did not see the field in his short stint up in Seattle. He was recalled Tuesday because Jorge Polanco was away on paternity leave. With Polanco returning Thursday, Rivas was sent back down Triple-A.

Analysis: Moore smacked an 87 mph slider off Tarik Skubal deep to right field in what was ultimately the game-winning home run. Two of Moore's three starts have come at second base, and his versatility to serve in the infield and outfield should allow him to see regular playing time in 2025.

Analysis: Robles got the Mariners on the board in the second inning with a double to center that brought J.P. Crawford and Dylan Moore across home plate. It was Robles' first RBIs since Opening Day against the Athletics, and the 27-year-old is on a five-game hit streak in which he's gone 6-for-21 with three doubles and two RBI.

Analysis: Munoz got off to a shaky start with two straight walks before recovering with a punchout. A Dillon Dingler single loaded the bases, but Munoz managed to close things out with a fielder's choice to home plate before striking out Zach McKinstry. Wednesday was a far more challenging effort than his first two outings, but Munoz has managed to earn three saves on as many opportunities without giving up a run. With the Mariners scheduled for an off-day Thursday, he should be available for the start of the three-game weekend road series against the Giants.

Analysis: Castillo limited the Tigers to three baserunners across the first four innings, but his shutout efforts were lost in the fifth frame when he gave up a solo homer to Trey Sweeney. Castillo gave up a second run in the same frame on a fielder's choice, but he managed to pitch into the seventh inning without much trouble and came away with the quality start and win. Castillo has started the season with a 3.00 ERA, 1.00 WHIP and 9:4 K:BB across 12 innings. He'll look for a second straight win in his next start, which is tentatively slated for next week against the Astros at home.

Analysis: Solano will pick up his third start of the season, all of which have come at first base and when the Mariners have gone up against left-handed pitching. The 37-year-old looks like he'll be limited to a short-side platoon role while Rowdy Tellez and Luke Raley are healthy and available to serve as the primary options at first base and designated hitter, respectively.

Analysis: Raley and fellow left-handed hitter Rowdy Tellez will move to the bench for the series finale while the Tigers send southpaw Tarik Skubal to the hill. With Raley getting the afternoon off, Cal Raleigh will occupy the designated-hitter spot while Mitch Garver fills in for Raleigh behind the plate.

Analysis: The Tigers are sending southpaw Tarik Skubal to the hill, so Tellez and fellow left-handed hitter Luke Raley will hit the bench as the Mariners add a couple of extra right-handed bats to the lineup. Donovan Solano will step in for Tellez at first base.

Analysis: Detroit got its hits in bunches, while Seattle managed only one hit the entire night off Casey Mize and the Tigers' bullpen -- a leadoff single by Victor Robles in the first inning. Gilbert was still dominant despite the lack of run support, generating 22 swinging strikes among his 92 pitches. The right-hander has an eye-popping 18:1 K:BB through his first 12 innings of 2025, and he'll look to keep rolling in his next outing, which lines up to come at home early next week against the Astros.

Analysis: With Jorge Polanco away on paternity leave, the Mariners will call up Rivas to give the team additional infield depth for the next several days. The 27-year-old turned in a .607 OPS in 86 plate appearances with the M's last season but has already blasted two home runs in three Triple-A games this year.

Analysis: Polanco will be allowed to miss up to three games while he spends time with his growing family. Miles Mastrobuoni will cover third base Tuesday, and Leo Rivas will come up from the minors to fill the open roster spot.

Analysis: Diaz's selection now makes Seattle's roster full at 40 players. He was beaten out by Emerson Hancock in spring training for a role in the starting rotation. With Hancock optioned to Triple-A Tacoma in a corresponding move Tuesday, Diaz will get a chance in the rotation.

Analysis: Hancock couldn't make it out of the first inning during his season debut Monday, surrendering six earned runs on seven hits and a walk while recording just two outs. He'll now head to Triple-A in order to right the ship, and Jhonathan Diaz will come up from Tacoma to take Hancock's place in the Mariners' rotation.

Analysis: Polanco isn't dealing with any known injury, but this is the second time in the last three days that his name has been missing from the lineup. Miles Mastrobuoni will start at third base and bat eighth for the Mariners on Tuesday.

Analysis: Seattle hasn't provided any official updates on Kirby's status since he was placed on the IL last week, but the right-hander was able to resume his throwing program March 21 after he was briefly shut down due to shoulder inflammation. Kirby is eligible to return from the IL next Tuesday, but he looks like he'll need more time beyond that to complete his throwing progression and get fully stretched out for starting duty. Emerson Hancock secured a spot in the Mariners' Opening Day rotation as a result of Kirby's injury.

Analysis: Although the game was relatively out of reach, Raleigh launched a two-run shot in the ninth inning to at least keep hope alive for the Mariners temporarily. The switch-hitting backstop hit just .186 over 59 at-bats during spring training, and he's gone just 2-for-17 with three walks and a stolen base in his first five games of the season.

Analysis: Arozarena took Tigers right-hander Jackson Jobe deep for a solo blast in the second inning. While the 30-year-old outfielder has just three hits in 20 plate appearances through his first five games, each has gone for extra bases. Arozarena has also drawn four walks, and the combination of the pop and patience at the plate has helped lead to a .975 OPS despite a .188 batting average.