Muller will start the first game of Monday's doubleheader with the Mets, David O'Brien of The Athletic reports.
Muller will face the unenviable task of opposing Mets ace Jacob deGrom in Game 1 of the twin bill, making it difficult to depend on the lefty rookie to come away with a win even if he pitches well in his first MLB start. Ian Anderson is slated to start Game 2 of the twin bill.