The Braves optioned Muller to Triple-A Gwinnett following Saturday's game against the Marlins.
The lefty has been decent, giving up no more than three runs in any of his three starts this season. Muller has a 3.45 ERA through 15.2 innings pitched, but apparently the Braves felt a greater need for a position player in Orlando Arcia, whom they recalled in a corresponding move.