Williams (appendicitis) was placed on the 10-day injured list Monday, Russell Dorsey of the Chicago Sun-Times reports.
Williams was scheduled to start Monday's game against the Padres but underwent an appendectomy Sunday. He doesn't have a timetable for his return, but he's scheduled to meet with a doctor Thursday, Gordon Wittenmyer of NBC Sports Chicago reports. Right-hander Kohl Stewart was recalled to start Monday's game, and he could continue to start in Williams' place until he's cleared to return.