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SEATTLE, WASHINGTON - OCTOBER 05: Luis Castillo #58 of the Seattle Mariners celebrates with teammates after being pulled from the game against the Detroit Tigers during the fifth inning in game two of the Division Series at T-Mobile Park on October 05, 2025 in Seattle, Washington. (Photo by Steph Chambers/Getty Images)

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With less than 48 hours remaining until Monday’s MLB trade deadline at 6 p.m. ET, deals are starting to fly in.

The latest came Saturday night when the Chicago White Sox and Seattle Mariners agreed to a blockbuster trade.

White Sox Acquire 3-Time All-Star

Chicago desperately needed starting pitching, and the front office addressed that need by acquiring three-time All-Star Luis Castillo from the Mariners.

The White Sox paid a steep price, sending reliever Seranthony Dominguez, outfielder Nolan Jones, and catching prospect Boston Smith to Seattle.

Breaking: The Chicago White Sox are acquiring right-hander Luis Castillo in a trade with the Seattle Mariners for reliever Seranthony Dominguez, outfielder Nolan Jones and catching prospect Boston Smith, sources tell @JeffPassan.

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— ESPN (@espn) August 2, 2026

The White Sox will also assume the remainder of Castillo’s contract, paying him $22.75 million this season and another $22.75 million in 2027.

Castillo’s 2026 Season

Castillo hasn’t looked like himself in 2026, but a change of scenery could help him rediscover his previous form.

He joins Chicago with a 3-9 record and a 5.06 ERA across 17 starts and 20 appearances this season.

Now in his 10th MLB season, Castillo may be showing signs of regression, though this could simply be an outlier year. He posted a 3.54 ERA last season, and over the course of his career, he has finished with an ERA above 4.00 only once.

White Sox Right Now

The White Sox have been one of baseball’s biggest surprises this season and, entering Saturday night, sit firmly in the American League playoff race.

Chicago is 58-52 and holds a 2.5-game lead over the Cleveland Guardians and a 3.0-game lead over the Minnesota Twins in the AL Central.

Castillo may not solve every problem, but he gives the White Sox another proven arm as they try to make a serious postseason push in an American League that appears wide open.