The Red Sox activated Sims (lat) from the 15-day injured list Thursday, Christopher Smith of MassLive.com reports.
Sims missed a little more than three weeks of time with a right lat strain but has been cleared to rejoin the Boston bullpen after making a couple rehab appearances with Triple-A Worcester. He's collected an 8.10 ERA in 11 outings for the Red Sox and will likely be pegged for middle relief.