The Cubs optioned Miller to their alternate training site Sunday.
Miller served as the Cubs' primary pitcher behind starter Colin Rea in the second game of Saturday's doubleheader against the Cardinals, pitching three innings of one-run ball. Since Miller tossed 34 pitches in the outing and was unlikely to be available for at least the next couple of days, the Cubs opted him to swap him out for a fresh arm in Matt Dermody, whose contract was selected from the alternate site in a corresponding move.