Kansas City placed Keller on the 15-day injured list Friday, retroactive to May 16, with right shoulder impingement syndrome.
Keller issued a whopping eight walks over just 3.2 innings in his last turn through the Royals' starting rotation Monday against the Padres. He's at 40 walks through 43.1 total innings this year. There is no timetable yet for the 27-year-old right-hander's return.