Nuno was optioned to Triple-A Norfolk on Sunday.
The struggling Nuno will be replaced in the Orioles bullpen by Richard Bleier, who was recalled from Norfolk in a corresponding move. The left-hander had given up runs in each of his last three appearances with the Orioles to inflate his ERA to 6.75 over 12 innings on the season, prompting the organization to send him back to the minors for further refinement.