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6/27/2013 6:42 P.M. ET

MRI shows Buchholz has shoulder inflammation

Red Sox right-hander shut down from all throwing activities until weekend

BOSTON -- Almost three weeks since he last pitched, Red Sox ace Clay Buchholz has been shut down for the next two to three days.

An MRI on his right shoulder revealed no structural damage, but it did show some inflammation in the bursa sac area. To let that inflammation subside down, Buchholz, who hasn't pitched since June 8 due to neck soreness, will not do any throwing until the weekend.

"He's in a couple-of-day shutdown period," manager John Farrell said. "We're hopeful that he'll initiate a throwing program likely on the weekend. He underwent the MRI yesterday, which didn't show any structural issues. He's got some inflammation in the bursa sac area, so structurally everything is good and I think that's the most encouraging thing at this point."

Farrell said Buchholz's return date is still in question and wouldn't rule out his absence extending beyond the All-Star break. With a 9-0 record and 1.71 ERA, Buchholz has been dominant when healthy, but an awkward throw to first base he made during his last start caused pain near his trapezius muscle, located at the base of the neck. Earlier in the week, Farrell hoped Buchholz could make a rehab start as early as Sunday, but when he throws from a pitcher's mound, the downward angle causes irritation in the problem area.

"He's felt it more as he decelerates or as he follows through," Farrell said. "It wasn't at the point at any acceleration or when his arm is traveling through the arm slot prior to release. It's always been after the release, and that's why as the intensity increased, the more you're having to put the brakes on. And that's where he was having the discomfort or not feeling like it was ready to ramp up to full game speed. So that's the sensation he's described to me."

Buchholz was forced to abandon a bullpen session after about 15-18 pitches Wednesday and had the MRI shortly after.

"It's just not quite there yet," Buchholz said. "Playing long toss, playing catch it feels fine. It's just that incline right now. It's not something that's a terrible feeling, it's just I want it to be gone. I don't feel like pitching, going out some starts and then having it flare up again."

Farrell was encouraged the MRI did not reveal any structural damage, and now that the Sox know exactly what the problem is, they have a better idea on how to treat it.

"In the past, we kind of reacted on how he felt on a given day," Farrell said. "There will be more structure as far as number of throws, prescribed distances just so we can track it more regularly in advance of getting back on the mound."

In Buchholz's absence, rookie Allen Webster will fill the rotation void. He has an 0-2 record with an 11.25 ERA in three starts this season and is scheduled to pitch Friday against Toronto.

With power numbers sagging, Napoli out of lineup

BOSTON -- As the Red Sox opened a four-game series against the Blue Jays Thursday, Mike Napoli was given a day off in favor of Mike Carp at first base.

Manager John Farrell said the move was just due to matchups, but there's no denying Napoli has seen a steep drop in his power numbers in June.

It's been 26 days and 64 at-bats since Napoli has hit a home run. Of his 31 extra-base hits this season, only two have come this month. Since June 1, Napoli has actually raised his average to .264 from .252, but Farrell said he has noticed a slight change in the first baseman's swing.

"I think at times you know the swing will get a little bit long at times, but that's no different than anybody else that's playing every single day," Farrell said. "If we can balance a day of rest in between to keep him fresh, that's in addition to a matchup that's kind of what we're looking to do."

Overall, Napoli is batting .264 with nine home runs and 53 RBIs.

Michael Periatt is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.