"Today, on the Minor League side, he had a clear step up without overexerting," manager John Farrell said. "We expect this stay to be minimal."
Boston has taken a slower approach with the 33-year-old Breslow this spring, learning from last year, when he was kept out of action until May 6 because of shoulder tendinitis.
"He put up a little bit of a fight. He felt like he could be ready for the start of the season," Farrell said. "We just felt like, similar to last year, we want to build his foundation."
A vital part of last season's championship run, Breslow threw 59 2/3 innings with a 1.81 ERA in 61 games in 2013.
Quinn Roberts is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.