The Rockies designated Stephenson for assignment Thursday.
The transaction clears a spot on the 26-man active roster for right-hander Chad Kuhl (hip), who was activated from the 15-day injured list with the expectation that he'll rejoin the rotation during this weekend's series with the Mets. Stephenson delivered underwhelming numbers while mostly working in a middle-relief role for the Rockies this season, producing a 6.04 ERA and 1.48 WHIP over 44.2 innings.