Montero was optioned to Triple-A Albuquerque on Sunday, Patrick Lyons of TheDNVR.com reports.
Montero earned his first big-league call-up Friday, and he made his MLB debut in Sunday's win over the Reds. He went 2-for-4 with two strikeouts but will head back to Albuquerque since the Rockies need to trim their active roster to 26 players by Monday. If Colorado deals with more injuries, it wouldn't be surprising to see Montero back in the majors at some point.