The Chicago White Sox on Thursday placed left-hander Dallas Keuchel on the 10-day injured list, retroactive to Sept. 7, with back spasms.
He left his start against the Kansas City Royals on Sunday with back soreness, and the team had already announced that he would miss his next turn in the rotation.
Keuchel is 6-2 with a 2.19 ERA this season, his first with the White Sox.
The 32-year-old has been dealing with back issues for much of the season and only went five innings in each of his past two starts.
He ranks among the American League leaders in ERA (second), opponent slugging percentage (second, .279) wins (tied for second), opponent OPS (third, .542) and walks per nine innings pitched (fifth, 2.03).