The Red Sox promoted Mullins from Double-A Portland to Triple-A Worcester on Tuesday.
Mullins is expected to make his Worcester debut with a start Wednesday in Game 1 or 2 of the club's doubleheader with Rochester, per Brendan Campbell of BloggingTheRedSox.com. Though the 25-year-old submitted a 5.85 ERA and 1.44 WHIP across 47.2 innings with Portland, he's been one of the Eastern League's most prolific strikeout artists this season, ranking second on the circuit with a 34.8 K%.