Mariners' Luis Castillo: Piggybacking Miller on Tuesday
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Castillo is slated to piggyback starting pitcher Bryce Miller during Tuesday's game against the White Sox, Adam Jude of The Seattle Times reports.
Castillo will be making the first relief appearance of his MLB career Tuesday after going 1-4 with a 6.34 ERA and 1.57 WHIP through his first nine starts of the season. Since Miller covered 5.1 innings in his 2026 Mariners debut last week in Houston following his return from the injured list, manager Dan Wilson is likely to let Miller work as long as he's effective against the White Sox. With that in mind, Castillo's innings projection for Tuesday is highly variable, and how he and Miller both perform could determine how Seattle sets up its rotation moving forward. If Miller comes through with a strong outing Tuesday, he'll likely draw another start the next time the fifth spot in the rotation comes up, while Castillo could be thrust into a more flexible bullpen role on a longer-term basis.
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Mariners' Luis Castillo: Finally gets into win column
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Castillo (1-4) earned the win Thursday against the Astros, allowing three runs on four hits and three walks in 5.2 innings. He struck out six.
Castillo was working on a bounce-back start Thursday, giving up a lone run over his first five frames, but the Astros got to him for two more runs in the sixth inning to make his line more middling. The Mariners might have left the 33-year-old right-hander in the game for a bit too long considering that the hurler tossed a season-high 108 pitches. Castillo has now yielded at least three runs in three straight outings and six of his last eight, posting a disappointing 6.34 ERA, 1.57 WHIP and 43:16 K:BB over 44 innings in 2026. He's tentatively lined up to piggyback with Bryce Miller early next week versus the White Sox, which would mark Castillo's first career relief appearance if he works as the secondary pitcher.
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Mariners' Luis Castillo: Tagged with another loss
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Castillo (0-4) was tagged with the loss Saturday against the White Sox, allowing four runs on five hits across four frames. He struck out six.
This loss against Chicago ballooned Castillo's woeful ERA to 6.57 across 38.1 innings in eight outings this year. He's lost his past three starts and has given up at least four runs in each of those games. Castillo has been confirmed to start Thursday against the Astros, but according to Ryan Divish of The Seattle Times, after that the Mariners plan to piggyback him with Bryce Miller in the rematch series against the White Sox that runs May 18-20.
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Mariners' Luis Castillo: Takes another loss
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Castillo (0-3) allowed four runs on six hits, two walks and a hit-by-pitch while striking out five over six innings to take the loss Sunday versus the Royals.
Castillo was doing fine until the fourth inning, when he allowed four straight batters to reach base to open the inning. Three of them came around to score, and the Royals tacked on an extra run in the sixth. Castillo has allowed at least four runs in five of his seven starts this season, though this is the third time he's allowed four earned runs. He has a 6.29 ERA, 1.66 WHIP and 31:13 K:BB through 34.1 innings. Until Castillo is able to limit baserunners better, he is likely to continue having trouble preventing runs. His next start is projected to be on the road versus the White Sox.
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Mariners' Luis Castillo: Fans six in no-decision
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Castillo tossed five innings against the Athletics on Tuesday, allowing two runs on five hits and two walks while striking out six batters.
Castillo gave up a run in the first inning and another in the fourth but kept Seattle in the contest throughout his time in the game. The right-hander wasn't very efficient, however, as he needed 95 pitches to complete five frames. That was partly because he had his swing-and-miss stuff working -- Castillo recorded 14 whiffs, and his six punchouts were his second most through five starts so far this season. The veteran hurler is still looking for his first victory, which he'll try to notch in what's projected to be a matchup versus Minnesota on the road his next time out.
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Mariners' Luis Castillo: Ineffective again Sunday
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Castillo allowed seven runs on 10 hits and one walk while striking out three batters over 3.1 innings in a no-decision against Houston on Saturday.
The Mariners gave Castillo a two-run lead in the first inning, but the veteran hurler fell behind when Taylor Trammell cleared the bases with a three-run double in the second. Castillo gave up three more runs in the third and another in the fourth before being pulled with one out in the latter frame. After tossing six scoreless innings against the Yankees in his first start of the campaign, Castillo has surrendered 11 runs (10 earned) over seven frames across his past two outings. He'll try to get back on track in his next start, which lines up to be a road outing in San Diego.
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Mariners' Luis Castillo: Struggles in no-decision
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Castillo did not factor into the decision Sunday against the Angels, allowing four runs (three earned) on six hits and one walk while striking out four over 3.2 innings.
Castillo couldn't find a rhythm in this one, allowing at least two baserunners in every inning he worked and exiting before completing four frames for the first time since 2024. The right-hander ran into trouble immediately, allowing a leadoff double to Zach Neto before Jorge Soler brought him home with an RBI single, and the outing didn't improve much from there. Unlike his dominant Opening Day outing in which he tossed six scoreless innings with seven strikeouts, Castillo failed to fool hitters Sunday and was consistently pitching under pressure. The 33-year-old will look to bounce back in his next scheduled start against Houston, though it presents a tough test against one of the league's most productive offenses early in 2026.
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Mariners' Luis Castillo: Dominates Yankees, reaches 1500 Ks
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Castillo did not factor into the decision Monday against the Yankees, allowing two hits and two walks while striking out seven over six scoreless innings.
Castillo was in complete control, holding the Yankees hitless until the fourth inning and limiting them to just two hits overall. The right-hander generated 17 whiffs and leaned heavily on his primary arsenal, throwing 87 of his 95 pitches as either a fastball or slider. Castillo had hitters fooled all night, but his final strikeout was a milestone moment, as he got Aaron Judge to swing through an inside breaking ball for his 1,500th career strikeout before exiting after the sixth inning. The 33-year-old will look to replicate Monday's success in his next scheduled start against the Angels.
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Mariners' Luis Castillo: Strong finish to spring slate
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Castillo allowed one run on four hits and a walk while striking out five across five innings in Monday's matchup with the Padres.
Castillo finished Cactus League play on a high note, allowing three runs over nine innings in his final two outings. It's certainly an encouraging development after the right-hander struggled to a 27.00 ERA in his first three appearances (six innings). Castillo, who's posted a sub-4.00 ERA in each of his last seven seasons, made a team-high 32 regular-season starts in 2025, finishing with a 3.54 ERA, 1.18 WHIP and 162:46 K:BB across 180.2 innings.
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Mariners' Luis Castillo: Short outing in ALCS
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Castillo (1-1) allowed three earned runs on five hits and one walk while striking out one across 2.1 innings to take the loss in Game 4 of the ALCS on Thursday.
Castillo got through two innings unscathed, but he allowed five of the first six hitters he faced in the third frame to reach base before being pulled. This was Castillo's first stumble of the postseason, as he had previously thrown six scoreless innings across two appearances in the ALDS. He has a less impressive 5:5 K:BB, but he has largely been a reliable arm for Seattle.
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Mariners' Luis Castillo: Dominates Rockies in 11th win
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Castillo (11-8) earned the win Wednesday against the Rockies, allowing one run on one hit and one walk in 7.1 innings. He struck out 10.
Castillo helped propel the Mariners to an American League West title, authoring one of his finest performances of the year. It was the first time this season that the right-hander piled up double-digit punchouts, and it was also his longest outing of the campaign. Castillo will be hoping to see most of his playoff action come at T-Mobile Park -- he'll close the regular season with a 2.60 ERA and 0.97 WHIP over 17 home starts versus a 4.71 ERA and 1.46WHIP across 15 road outings.
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Mariners' Luis Castillo: Blanks Royals in 10th win
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Castillo (10-8) earned the win Thursday against the Royals, allowing three hits and striking out three across six scoreless innings.
Castillo allowed only three baserunners through his six innings of work, leaning heavily on his breaking pitches -- mixing in 20 sliders and 16 changeups -- to induce weak contact. The right-hander was at 40 pitches through two innings but settled in nicely, needing just 84 pitches overall to log his third straight quality start. Castillo has been overall sharp in September with a 2.86 ERA across four outings and will look to keep it going in his final start of the regular season next week against the Rockies. While Colorado has reached base at the lowest rate in MLB this month, the hitter-friendly environment at Coors Field is always a factor.
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Mariners' Luis Castillo: Bounces back in ninth win
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Castillo (9-8) earned the win over Atlanta on Sunday, allowing one run on four hits and no walks across six innings. He struck out six.
It was a much-needed outing for Castillo, who earned his first win since July 28 -- he'd struggled to a 10.06 ERA in his previous four starts (17 innings). Overall, Castillo's ERA sits at 3.85 on the year with a 1.27 WHIP and 144:44 K:BB through 29 starts (161.1 innings). Castillo will look to build on Saturday's effort his next time out, currently lined up for next week against the Angels.
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Mariners' Luis Castillo: Skid continues Monday
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Castillo (8-8) allowed five runs on six hits and a walk while striking out five over four innings to take the loss versus the Rays on Monday.
Castillo was held under the five-inning mark for the third time in his last four starts. In that span, he's surrendered 19 runs over 17 innings, including six home runs, one of which came off the bat of Nick Fortes in the second inning of Monday's contest. Castillo is also winless in his last six outings, though he's taken just two losses in that span. For the season, he's now at a 3.94 ERA, 1.29 WHIP and 138:44 K:BB through 155.1 innings over 28 starts. He'll look to get back on track over the weekend in a road start at Atlanta.
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Mariners' Luis Castillo: Ambushed early in no-decision
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Castillo did not factor into the decision Tuesday, allowing five runs on five hits and three walks over five innings in a 7-6 loss against San Diego. He struck out six.
Castillo ran into immediate trouble Tuesday, surrendering all five of his earned runs in the first inning, punctuated by a Ramon Laureano grand slam. The 32-year-old hurler has hit a rough patch, pitching to a 5.45 ERA and 1.51 WHIP over 36.1 innings in his past seven starts. He's lined up to next take the mound Monday at Tampa Bay.
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Mariners' Luis Castillo: Settles for no-decision Friday
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Castillo didn't factor into the decision in Friday's 3-2 win over the Rays, giving up two runs on five hits over seven innings. He struck out five without walking a batter.
All the damage off the veteran righty came on solo shots by Brandon Lowe in the first inning and Junior Caminero in the sixth, but all of Seattle's offense came on a three-run blast by Cal Raleigh in the eighth. Castillo delivered his 14th quality start of the year on 99 pitches (72 strikes), and he's allowed three earned runs or fewer in eight straight trips to the mound, posting a 2.25 ERA, 1.02 WHIP and 45:7 K:BB through 48 innings over that span. He'll look to get back in the win column in his next outing, which is scheduled to come on the road next weekend against the Mets.
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Mariners' Luis Castillo: Labors in no-decision
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Castillo did not factor into the decision in Saturday's 6-4 extra-innings loss to the Rangers, allowing two runs on four hits and one walk with four strikeouts over 4.1 innings.
Castillo allowed both of his runs in the third inning and failed to complete five frames for just the second time in 23 starts, throwing only 51 of 87 pitches for strikes. Still, the veteran has now surrendered three earned runs or fewer in seven straight outings, a stretch that includes four wins and four quality starts. He'll take a 3.22 ERA, 1.21 WHIP and 115:37 K:BB across 131.1 innings into a home matchup with the Rays next weekend.
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Mariners' Luis Castillo: Falls to Milwaukee
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Castillo (7-6) took the loss Wednesday against the Brewers, allowing six runs (three earned) on 10 hits over five innings. He struck out seven.
The 10 hits allowed matched a season high for Castillo, who would take his first loss since June 18 -- the right-hander had pitched to a stellar 1.46 ERA in four starts (24.2 innings) prior to Wednesday. Overall, Castillo sports a 3.30 ERA with a 1.24 WHIP and 107:36 K:BB over 21 starts (120 innings) this season. He'll look to get back on track in his next outing, currently scheduled for next week against the A's.
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Mariners' Luis Castillo: Picks up win in one-sided victory
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Castillo (6-5) earned the win Friday, allowing three runs on six hits and two walks over five innings while striking out six in the 12-3 victory over the Tigers.
Castillo shined early, yielding just one earned run through the first five innings before running into trouble opening the sixth, allowing back-to-back hits and another run before being removed with a runner on third. The 32-year-old entered the matchup coming off his best start of the season and has now posted a 3.60 ERA with 33 strikeouts and 11 walks over his last six outings.
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Mariners' Luis Castillo: Turns in quality start
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Castillo allowed two runs on three hits and three walks while striking out seven over six innings in a no-decision Friday versus the Guardians.
Castillo was able to limit the damage to back-to-back solo home runs by Nolan Jones and Steven Kwan in the third inning. After allowing just four homers in his first 12 starts of the year, Castillo has given up five long balls over his last two outings. On the positive side, Friday's effort was his eighth quality start, five of which have come over his last six games. Castillo has a 3.29 ERA, 1.27 WHIP and 67:26 K:BB through 79.1 innings this season. The veteran right-hander is projected to make his next start at home versus the Red Sox.
