Hanrahan has been hampered by lingering right hamstring soreness, so evidently the issue wasn't getting any better with just a few days rest.
Hanrahan, 31, has saved three of his four chances this season with an 11.57 ERA, 2.36 WHIP and five walks compared to four strikeouts in 4 2/3 innings. He's also allowed three homers in just 4 2/3 innings. In fairness, though, most of that damage came in a disastrous April 10 outing against the Orioles.
With Hanrahan on the shelf, Andrew Bailey steps in as closer for Boston. Considering he has 81 career saves, is a two-time All-Star and is off to a good start (1.69 ERA, 0.94 WHIP, 9 K in 5 1/3 IP) this season, it should be an easy transition.
As a corresponding move, the Red Sox have promoted right-hander Steven Wright from Triple-A Pawtucket. Wright, 28, finally makes the majors after being in the minors since 2007. He was 10-7 with a 2.54 ERA and 1.26 WHIP in 25 starts last season across both Double-A and Triple-A. So far this season in two Triple-A starts he's 1-0 with a 2.70 ERA and 1.30 WHIP.
Also, Wright is a knuckleballer. So that's fun.
News of Hanrahan heading to the DL was first reported by Peter Gammons.