Castillo will make his White Sox debut Thursday in Boston, James Fegan of SoxMachine.com reports.
After making his final start for the Mariners on Tuesday before being dealt to the White Sox on Saturday, Castillo will be well-rested and will have some extra time to get acclimated before debuting for his new organization. A three-time All-Star, Castillo brings ample experience to the White Sox rotation, but he submitted a 5.06 ERA and 1.39 WHIP -- both career-worst marks -- over 99.2 innings for the Mariners this season. He's been especially stung by the long ball recently, surrendering seven home runs over his last three outings after giving up just two total in his eight appearances before that.