Dustin Pedroia has his right thumb in a cast and is expected to miss at least three weeks.
His thumb was hyperextended on Tuesday when he tried to make a diving catch in shallow right field.
According to the Red Sox, Pedroia has a "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. "Then I should be healed enough to go out there and play. But I'm still getting another opinion."
Pedroia had X-rays and an MRI on Thursday and 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.
Pedroia has been treated by Sheridan 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 taken on Thursday.
"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 on Tuesday when he dove 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."
The Red Sox are starting Nick Punto at second base Friday night.