It has been a frustrating ordeal for Donnelly, who last pitched for the Red Sox on June 10.
"I can't even tell you," said Donnelly, who at that point ended his session with reporters.
"He did his long-toss [on Friday night]," said manager Terry Francona. "About 15 [minutes] into it, he just didn't feel great. No stabbing pain. Jim Rowe [from the training staff] was there with him. Threw a couple of splits, a couple of breaking balls. The decision was made to not pitch, which was obviously a very good decision. We're kind of stuck in neutral. We need to find out some answers."
Drew not in lineup: On Saturday, a day after being removed in the fourth inning with recurring tightness in his right hamstring, right fielder J.D. Drew was out of the lineup. Eric Hinske spotted Drew in the lineup and batted eighth.
When Francona spoke to the media before the game, he hadn't yet had a chance to confer with Drew.
"I think we're all very hopeful that he's going to feel great, but I have not spoken to him," Francona said.
Sticking with Tavarez: Though Julian Tavarez has struggled with his command in his last four starts, Francona said there is no thought of taking the right-hander out of the rotation.
"I agree that the last four starts haven't been real pretty, and it's kind of surprising," Francona said. "Watching Julian pitch, the more he pitches, you would think the more he'd command. He's kind of that sinker/slider guy, where touch and feel is so important. He's throwing hard. I think if anything, his two-seamer last night was kind of flat and up in the zone."
Rejuvenated Timlin: With Donnelly's latest setback, the timing of Mike Timlin's revival could not be better. Timlin has been unscored upon in his last seven outings. During that span, his ERA has gone from 6.48 to 4.00.
"We said all along, when you come back from various injuries, there's a lot of inconsistent innings," said Francona. "We wanted to get his innings consistent where he could help us, and that's what's happening right now. And he's done it in a variety of roles. I kind of go back to, if your guys are getting people out and you're winning, you don't hear guys complaining about when they pitch. Mike has never been like that. He just likes to pitch. He's gotten a lot of people out lately, and it's very, very welcome."
Coming up: Ace Josh Beckett (12-3, 3.44 ERA) makes his first start of the second half in the finale of this four-game series against the Blue Jays on Sunday at 2:05 p.m. ET. He'll be opposed by right-hander Jesse Litsch, who is 1-3 with a 4.74 ERA.