The Royals placed Clarke on the 15-day injured list Tuesday with a left oblique strain.
Clarke will be eligible to come off the IL on Aug. 23, but given the volatile recovery timelines associated with oblique injuries, he's far from a lock to be ready to rejoin the Royals by then. The 29-year-old right-hander has been a key setup man for the Royals this season, logging 10 holds and two saves while generating a 4.02 ERA and 1.19 WHIP in 47 innings over his 44 appearances.