Luis Castillo, who has struggled since trade from Mariners, lands on White Sox IL

What has been a rough stretch with his new team just became even more so for former Seattle Mariners right-hander Luis Castillo.

All the ways to celebrate Rick Rizzs in final series as voice of M’s

The Chicago White Sox placed Castillo on the 15-day injured list Thursday with a right shoulder impingement, likely ending the veteran starting pitcher’s season.

It’s been a struggle for the 33-year-old Castillo since he was sent to the White Sox as a part of a four-player deal that netted the Mariners reliever Seranthony Domínguez, outfielder Nolan Jones and catching prospect Boston Smith. In nine appearances for Chicago, he has an 8.42 ERA and 1.81 WHIP over 31 innings. His ERA is the highest among MLB pitchers who have thrown at least 30 innings since he was traded Aug. 2.

Castillo’s struggles led to White Sox attempting to use an opener for him in a start on Sept. 12 against St. Louis, but he surrendered three runs over 2 2/3 innings during the outing and was moved to the bullpen afterwards. Castillo made two relief appearances after the demotion, including allowing four runs over one inning in his most recent outing Tuesday against Kansas City.

Castillo was acquired by the White Sox with hopes he could be the missing piece in their rotation that could help them earn their first postseason berth since 2021. While his struggles haven’t helped, club clinched a playoff spot Thursday afternoon and is currently holding the American League’s final wild-card berth with an 81-77 record – 3 1/2 games ahead of Houston. The White Sox are also just one-half game behind Cleveland for first in the AL Central.

The IL stint will keep him out through at least the AL Division Series, but he would be eligible to return if the White Sox reached the ALCS.

A Bani, Dominican Republic, native, Castillo spent parts of five seasons with the Mariners following a 2022 trade deadline blockbuster that helped the club end its 21-year playoff drought. He posted a 43-40 record and 3.69 ERA over 718 innings pitched in 126 career appearances (123 starts) for Seattle. He is 10th all-time in team history with 719 strikeouts.

Mariners pitchers reflect on impact of Luis Castillo

Castillo is due to make $24.15 million next season in the final of year of his contract, which also includes a $25 million vesting option for 2028 if he pitches at least 180 innings next season.

While the Mariners have gone the wrong direction since the trade, their end of the deal has worked out better. Domínguez has a 3.18 ERA and 1.15 WHIP in 23 games since joining the Mariners, and has allowed just one earned run with 13 strikeouts to three walks over his last eight appearances. Smith, meanwhile, is a prospect on the rise who hit nine home runs in 33 games for Double-A Arkansas after the trade, finished the minor league season with 31 homers across three levels, and is set to play in the Arizona Fall League next month.

Seattle Mariners news and more

• Mariners Injury Report: Brendan Donovan, Matt Brash, Colt Emerson, more
• Has J.P. Crawford made the case for a Mariners return in ’27?
• Seattle Mariners prospect Felnin Celesten named Northwest League MVP

Related

Mariners officially eliminated from playoff contentionMariners put rookie on injured list, recall infielder Leo RivasAll the ways to celebrate Rick Rizzs in his final series as voice of the MarinersThe Mariners are still alive, with one slim path to playoffs remainingM’s fend off elimination with 6-5 walkoff over Astros in 10 inningsMariners’ Cal Raleigh reveals special Rick Rizzs chest protector he will wear