Zimmermann was recalled from Triple-A Norfolk on Sunday.
Zimmermann will return to provide length for what is essentially a bullpen game Sunday, headed up by Adam Plutko. The long ball has been a problem for Zimmermann at the highest level; he has given up nine homers in 37 big-league innings. The lefty has a 5.40 ERA and 1.63 WHIP for the Orioles this season.