The second baseman has a hyperextended right thumb and is expected to miss at least three weeks after being put in a cast. He was injured Tuesday trying to make a diving catch.

According to the Red Sox, Pedroia has “an injury to the volar plate” of his thumb. The volar plate is a thick ligament that prevents the thumb from being hyperextended.

“I’ll be in the cast for a couple of weeks,” Pedroia said Friday. “Then I should be healed enough to go out there and play.”

Pedroia had X-rays and an MRI Thursday and was examined by team doctors. The results of his tests will be sent to two specialists — Dr. Donald Sheridan in Phoenix and Dr. Thomas Graham in Cleveland — to get their opinions.

Sheridan has treated Pedroia before. Graham has done a number of hand-related surgeries on Red Sox players in recent years.

The torn adductor muscle on the inner part of Pedroia’s thumb, which occurred in May, has healed according to the MRI. “It’s frustrating,” Pedroia said. “I healed up from the other injury and I was just starting to feel better and swinging the bat better. I dive one time and now this. It’s just frustrating. But the guys will hold it down. We’re getting our other guys back and I’ll be back soon. We’ll make our run.”

Pedroia said no surgery is needed and the injury will not end his season.

“Heck no,” he said.

Pedroia was injured in the fifth inning Tuesday when he dived for a ball hit by Oakland’s Kurt Suzuki. At the time, he felt no unusual pain, but that changed after the game.

“It was kind of a freak accident,” Pedroia said. “It’s just a bad break. I’m pretty frustrated by it. You work so hard in the offseason to prevent injury and you get a couple of freak accidents in the same thumb. It stinks. But I’ll be fine. I’ll produce in a major way this season to help our team. I promise you guys that.”

Pedroia said the muscle tear had healed to a point where he was driving the ball with his usual authority.

“I was hitting the ball in the air to the pull side and using my hands. That’s the part that I have trouble dealing with. I played that month hurt and then I finally get healthy and I dive and get hurt again,” Pedroia said. “But I’ll be fine. It happens for a reason. I’ll be back.”

Bobby Valentine would not speculate on Pedroia’s return. “We’re not going to start counting days,” Valentine said. “I guess everybody who has to give an opinion is trying to give that. When a guy’s on the disabled list, he’s on the disabled list. I don’t plan on him coming back until someone says, ‘Hey, he looks good and he’s ready to come back.’ ’’

Middlebrooks betterWill Middlebrooks was out of the lineup for the fourth straight game with a strained left hamstring, but the rookie third baseman took batting practice and is hopeful of playing one of the games of Saturday’s doubleheader.

“I’m getting there,” Middlebrooks said. “I’m not taking ground balls today, but maybe tomorrow. The running went pretty well. I’m not there yet. Could I play? If I needed to.”

Buchholz improvingClay Buchholz, who has been on the disabled list since June 20 with a stomach ailment that caused internal bleeding, threw in the bullpen.

“He’s feeling great,” Valentine said. “After the break he’ll either slot in the first rotation or early in the second rotation depending on whether we and he feel he should get on the mound and pitch to some hitters [in a minor league game] before then or not.”

Crawford at Triple ACarl Crawford will move his rehabilitation assignment to Triple A Pawtucket Saturday. The PawSox host Syracuse at 6 p.m. Crawford has played in eight games and has 31 plate appearances as he returns from left wrist and elbow injuries.He said the platelet-rich plasma injection in his left elbow did not really help his partially torn ligament, but he has learned to throw adequately.

“It’s not 100 percent healthy but I’m able to hit,” Crawford said. “The elbow, there are still some issues. I’ve been making some throws down in the minor leagues, good enough to hit the cutoff man. I don’t know if I’ll be hosing anybody out at home or anything like that.

“But I think it’s strong enough to hit the cutoff man if I can get to the ball quick enough to stop the guys from advancing.”

Crawford could need surgery come the offseason.“Probably,” he said. “I’m at a point now where I can get by with it. So I’ll do that.”Crawford is hopeful of joining the Sox after the All-Star break.McDonald returnsFormer Red Sox outfielder Darnell McDonald, who was claimed off waivers by the Yankees on Wednesday, was in uniform for the visiting team. He played the ninth inning in left field.“It’s another one of those situations, it’s a dream,” McDonald said. “I’m playing against my old team. Not many times when that happens, when you get released and get a chance to play against the team that released you. To be able to come to another historic franchise like the Yankees is, again, it’s a dream come true for me.”

Ortiz honoredTwo days after he again complained about playing with a one-year contract, David Ortiz was honored before the game for hitting his 400th career home run. Team owners John Henry and Tom Werner, president Larry Lucchino, and Mayor Thomas M. Menino presented Ortiz with a plaque in the shape of home plate that listed all his home runs. Ortiz hugged the owners . . . The Red Sox called up infielder Pedro Ciriaco, who was hitting .301 with 21 RBIs and 14 steals for Pawtucket.