The Diamondbacks optioned Bratt to Triple-A Reno on Sunday, Alex Weiner of ArizonaSports.com reports.
Bratt was added to the 40-man roster in November but has yet to pitch at the Triple-A level, so he was never a likely bet to begin the campaign in the majors. The 22-year-old lefty may not have to wait too long to make his MLB debut, however, especially if he can duplicate the 3.38 ERA and 10.9 K/9 he produced at the Double-A level last year.