The Rays placed Thompson on the 15-day injured list Tuesday with right triceps inflammation, Neil Solondz of the Rays Radio Network reports.
A best-case scenario has Thompson returning around the middle of September, although it's unclear how significant his injury is. The sidearm-throwing righty hasn't pitched since Thursday, when he allowed two runs on four hits versus the Angels. Thompson sports a modest 3.80 ERA and 39:11 K:BB this season.