Carreras was designated for assignment by the Rockies on Sunday, Luke Zahlmann of The Denver Gazette reports.
The 24-year-old was optioned to Triple-A Albuquerque in mid-March and has now lost his place on the 40-man roster. Carreras has struggled to a .515 OPS and 32.9 percent strikeout rate through 38 games with the Isotopes this season.