The Red Sox activated Sims (lat) from the 15-day injured list Thursday, Christopher Smith of MassLive.com reports.
Sims (lat) walked two and recorded a strikeout in one-third of an inning in his first rehab appearance with Triple-A Worcester on Sunday.
The Red Sox placed Sims on the 15-day injured list Tuesday with a right lat strain, Pete Abraham of The Boston Globe reports.
Sims allowed one run on two hits and two walks while striking out one over one inning, picking up a blown save in Monday's 5-4 loss to Houston.
Sims allowed one walk over a scoreless two-thirds of an inning in Wednesday's 3-2 extra-inning win over Seattle.
The Red Sox acquired Sims from the Reds on Tuesday in exchange for Ovis Portes, Robert Murray of FanSided.com reports.
Sims allowed one hit and one walk over a third of an inning in Saturday's 4-3 win over the Cubs.
The Reds and Sims avoided arbitration by agreeing to a one-year, $2.85 million contract Thursday, Gordon Wittenmyer of The Cincinnati Enquirer reports.
Sims (3-2) was tagged with Sunday's loss to the Brewers. He allowed two runs on one hit and one walk over two-thirds of an inning.
Sims (3-1) picked up the win over Milwaukee on Saturday. He allowed one walk and struck out two over 1.1 scoreless innings.