The Brewers placed Milner on the 15-day injured list Sunday due to a left shoulder impingement.
It's unclear when the injured surfaced for Milner, but manager Pat Murphy noted that the southpaw was experiencing a loss of range of motion and strength, according to Sophia Minnaert of Bally Sports Wisconsin. The injury likely contributed to Milner's recent struggles, as he had surrendered five runs over two frames in his last two outings. The left-hander will be eligible to be reinstated in late August, though it's unclear how long he's expected to be sidelined.