Starting pitcher Luis Castillo's time with the Seattle Mariners has come to an end after he was traded to the Chicago White Sox on Saturday, the team announced. The Mariners will receive right-handed relief pitcher Seranthony Dominguez, outfielder Nolan Jones and catching prospect Boston Smith from the White Sox in exchange for Castillo. Castillo is also on an affordable contract, though his 5.06 ERA and brief demotion from Seattle's rotation makes him less attractive. The Mariners were largely banking on their main core maintaining the level of play they were at in 2025. As for the White Sox, they are getting one of the best and most reliable starters in baseball for the next three seasons.