Ashby was placed on the 15-day injured list with left shoulder inflammation Monday, retroactive to Aug. 20.
Ashby struggled during Friday's start against the Cubs, giving up six runs on eight hits and no walks while striking out eight in five innings. It's possible that his injury contributed to his struggles, and he'll ultimately be forced to miss time. The Brewers haven't yet indicated who will take Ashby's place in the rotation, but Adrian Houser (elbow) could come off the injured list this week.