Sims was optioned to Triple-A Gwinnett on Thursday.
The right-hander has lost his once promising prospect stock, having put together ERAs no lower than 4.20 over his last three combined minor league seasons. At this point the 22-year-old is looking more likely to relieve than start for the Braves, but his fastball/curveball combo could be devastating out of the bullpen if he can display even fringe average command.