Sims (back) will begin a rehab assignment Sunday with Triple-A Louisville.
Since Sims' placement on the IL is retroactive to March 27, he'll be eligible for activation as soon as Tuesday, but it's unclear if he'll be immediately reinstated at that time. The Reds will likely wait and see how he fares during his upcoming appearance Sunday before deciding whether he's fit to join the big-league bullpen or requires at least one more outing in the minors. Once activated, Sims is expected to settle into a setup role in front of closer Alexis Diaz.