The Red Sox optioned Rivera to Triple-A Worcester following Wednesday's doubleheader against the Orioles, Tim Healey of The Boston Globe reports.
Rivera drew the start in the second game of the twin bill but was unable to escape the first inning, coughing up four runs on three hits and two walks while recording two outs in 41 pitches. His demotion will free up a spot in the rotation that will likely be filled by Ranger Suarez (groin/illness) during Boston's upcoming series against Toronto. Until then, Alec Gamboa will remain with the big club to provide additional depth to the bullpen.