Dustin Pedroia (thumb) not starting

Boston Red Sox second baseman Dustin Pedroia is out of the lineup for Wednesday's series finale against the Oakland Athletics.

Pedroia's right thumb, which forced him to miss six games earlier this year due to a torn muscle, was sore after Tuesday's 3-2 loss to the A's.

"It's not in the area where I first got hurt," Pedroia said. "I don't know what happened."

Pedroia hadn't tried to swing a bat yet Wednesday, but felt he could pinch hit if necessary.

"They told me not to do anything," Pedroia said. "But if they need me to hit, I'll hit."

He believes the soreness was a result of diving for a ball in right field.

"I was fine during the game, and then after the game, I was hurting a little bit," Pedroia said. "I don't know. It's just frustrating."

Pedroia will have two full days' rest with Thursday's off day and will undergo further tests from a team doctor.

Pedroia and manager Bobby Valentine expect he'll be available for Friday's series opener at home against the New York Yankees.

There was no update on the left hamstring injury of third baseman Will Middlebrooks. For the third straight day, Valentine simply said Middlebrooks was feeling better than before, but he remained out of the lineup.

Valentine said he "had no idea" if Middlebrooks would avoid the disabled list. Such a move would be retroactive to Sunday, when Middlebrooks last played.

Mauro Gomez, who was called up Tuesday when Daisuke Matsuzaka was placed on the DL, was to start at third base Wednesday. Gomez has played 71 games in the minor leagues at third base and committed 31 errors. He hasn't played third base since 2009.

"He came up as a third baseman. He's been working out there all year," Valentine said. "I guess (he's got) as much experience as anybody else on our roster."

Outfielders Carl Crawford, Jacoby Ellsbury and Scott Podsednik continue to progress in their rehab stints.

Podsednik could be activated for this weekend's series with the Yankees. He went 1-for-2 with an RBI and two walks for Triple-A Pawtucket on Tuesday night.

Crawford and Ellsbury could be ready when the Red Sox return from the All-Star break July 13 at the Tampa Bay Rays. Crawford went 2-for-4 with an RBI on Wednesday in his second game with Double-A Portland. His first five rehab games came with the GCL Red Sox.

Ellsbury made his first appearance for Portland on Wednesday, going 1-for-5 while playing center field. He was 2-for-10 with a home run, a double, three RBIs and four walks in four rehab games with the GCL Red Sox.

Outfielder Ryan Sweeney, who is on the 15-day disabled list, will likely begin a rehab stint Thursday with Portland. He's been with the major league team on its current road trip and is expected to report to Portland after returning home to Boston with the club.

Pitcher Justin Germano officially joined the Red Sox on Wednesday, taking the roster spot of reliever Clayton Mortensen, who was optioned to Triple-A.

Germano was 9-4 with a 2.40 ERA as a starter for Triple-A Pawtucket. He had a July 1 opt-out clause in his minor league contract if he wasn't called up to the majors.

"I think it helped. Definitely put a little pressure on them," Germano said of the opt-out clause. "I wanted to see where they were at and if they thought they had a place for me. And if they didn't, I had to look out and see if there was a better opportunity elsewhere."

Germano most recently pitched in the majors for parts of the 2011 season with the Cleveland Indians. Valentine expects him to serve as the long man out of the bullpen.