"It's something I've been able to fight through, but it's kind of been a process where after I throw, it's pretty sore," O'Sullivan said, "then just kind of work to getting back to being game ready by Day 5. This last one was kind of tough, especially in that fourth and fifth inning. It got real hard to post up. It was my land leg."
O'Sullivan (2-0, 6.75 ERA), who has made five appearances (four starts) for the club this season, has been a consistent presence in the Red Sox's rotation since being recalled on July 3. He allowed four runs on seven hits in five innings for the no-decision on Friday against the Rays.
With the upcoming All-Star break, O'Sullivan and the Red Sox thought it was the right time to allow his knee to heal.
"With the break and everything coming up, I think they saw it as an opportunity to get my knee a chance to calm down," O'Sullivan said. "Hopefully, we can move all the way past it and not let it affect any more outings."
Quinn Roberts is a reporter for MLB.com based in Boston. This story was not subject to the approval of Major League Baseball or its clubs.