Otto was optioned to Triple-A Round Rock on Tuesday.
Otto failed to win a spot in the Opening Day rotation but remains one of the team's top candidates to call on when they need another starter. The 26-year-old was knocked around to the tune of a 9.26 ERA in his six-start debut last season, but that hid a promising set of peripherals, as he was slightly better than average in all three of strikeout rate (25.2 percent), walk rate (7.2 percent) and groundball rate (44.4 percent).