Ashby (shoulder) was placed on the 15-day injured list Wednesday, Adam McCalvy of MLB.com reports.
Ashby is likely to miss the first six weeks of the regular season while recovering from the left shoulder injury, and he has yet to return to throwing bullpens after being diagnosed with a partial tear and impingement of his labrum. The southpaw could make starts for the Brewers upon his return, but Milwaukee might ease the 24-year-old back into action.