Castro, who was traded to the Orioles on Friday, was optioned to Double-A Bowie, Brittany Ghiroli of MLB.com reports.
Prior to being traded to the Orioles, Castro split time last season between the Triple-A and big-league levels with the Rockies. However, it appears the Orioles plan to slow things down a bit for the 22-year-old right-hander by assigning him to Double-A Bowie.