The Rays designated Heller for assignment Friday, Ryan Bass of Bally Sports Sun reports.
Just over a week after being selected from Triple-A Durham, the 31-year-old righty will lose his spot on the Rays' 40-man roster following the acquisition of Robert Stephenson from Pittsburgh. Heller holds a 3.95 ERA and 1.40 WHIP in Triple-A this season through 27.1 innings and could be claimed by another team in need of organizational bullpen depth.