The Red Sox placed Giolito (hamstring) on the 15-day injured list Thursday, Mac Cerullo of the Boston Herald reports.
Giolito tweaked his hamstring during his first start of the spring back in mid-March. He was never shut down from throwing, and he most recently threw a two-inning simulated game at the Red Sox's spring training complex Sunday, according to MLB.com. The Red Sox appear optimistic that the right-hander won't miss much more than two or three turns through the rotation before making his team debut at some point in April.