Mariners' Luis Castillo continues to struggle in loss to White Sox

Ryan Divish, The Seattle Times on May 9, 2026

Published in Baseball

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CHICAGO — In what has been a curiously uneven and far too inconsistent start to the highly-anticipated 2026 season, two of the prohibitive factors in the Mariners’ issues — the struggles of Luis Castillo and the offense’s inability to hit left-handed pitching — came together Saturday night at Rate Field.

The results — a 6-1 loss to the White Sox — were somewhat predictable.

Castillo, whose spot in the starting rotation is tenuous at best, pitched four innings, allowing four runs on a pair of two-run homers while forcing the Mariners to play from behind almost immediately,

Meanwhile, White Sox starter Anthony Kay, a soft-tossing lefty who spent the last two seasons pitching in Japan, stymied Seattle’s offense in his outing. Kay, who came into the game with a 5.70 ERA in five starts and two relief appearances, pitched five innings, allowing one unearned run on three hits with two walks and five strikeouts to improve to 2-1 on the season.

The Mariners are now 5-8 in games started by left-handed pitchers this season.

Kay came into the game with a 5.70 ERA. In 30 prior innings pitched, he’d allowed 35 hits, including six homers with 15 walks and 20 strikeouts. Opponents had put up an .897 on-base plus slugging percentage vs. Kay.

Was one aspect more at fault?

In his previous outing against the Royals, Castillo gave the Mariners a reason to hope there were better outings ahead. His fastball velocity was back up in the mid to high 90s and his stuff actually looked lively even though he still allowed four runs on six hits over six innings pitched.

Castillo’s velocity wasn’t quite as good as his previous outing and it declined a tick or two with each inning he worked. It was noticeable in his inability to finish off a few hitters. He still struck out six batters, but his efficiency wasn’t ideal. Chicago hitters fouled off 22 pitches in his outing, including 12 with two strikes. He needed 65 pitches to get through the first three innings.

Sam Antonacci led off the game with a single. Later with two outs, Castillo got up on Colson Montgomery 0-2. But a pair of sliders — one for a ball and another fouled — never got the swing and miss to end the inning. Castillo tried to elevate a fastball, but it wasn’t above the zone enough. Montgomery stayed on top of the ball, sending it into the right-field seats for a 2-0 lead. It was Montgomery’s 10th homer of the season.

Chicago made it 4-0 in the third inning. Castillo hit Antonacci with a 2-2 sinker to start the inning. With one out, Miguel Vargas ambushed a first-pitch sinker that was on the inner part of the plate, sending it over the wall in left for a 4-0 lead.

Meanwhile, the Mariners offense which scored 12 runs roughly 24 hours earlier, did little against Kay, even when they did get runners on.

The Mariners’ lone run came in the fifth inning. Mitch Garver worked a leadoff walk and Cole Young reached on an error by first baseman Munetaka Murakami. Despite being down four runs, Leo Rivas bunted the runners over. Rob Refsnyder hit a hard line drive to left that was caught on a tough catch by Antonacci, but Garver was still able to tag up and score from third.