An MRI on Bailey, 28, showed no structural damage, according to MLB.com. The right hander will likely be able to return as soon as the fifteen day minimum is up. Bailey has not pitched since April 28, so he will be eligible to return on May 14.
In the interim, Joel Hanrahan will likely take over the ninth inning. Hanrahan, 31, had been the closer in Boston before ineffectiveness and his own DL stint allowed Bailey to steal the job. Hanrahan, acquired from the Pirates in the offseason, collected the Red Sox's only save opportunity since Bailey's injury.
Bailey has been excellent this season, posting a 1.46 ERA over 13 games with a phenomenal 14.6 K/9 and 0.811 WHIP. He was also a trade acquisition, being brought over from the Oakland Athletics prior to the 2012 season. Bailey was expected to be the Red Sox closer moving forward, but missed much of last season due to injury and generally pitched poorly when he was healthy. Prior to that, he had three very good seasons for the Athletics.
Breslow has not pitched this season after suffering a shoulder injury. He has been a good reliever over his career, posting a 3.00 ERA over 358 games. Last season he had a 2.70 ERA and was traded midseason from the Arizona Diamondbacks to the Red Sox. Breslow will slot into Bailey's spit in the bullpen.