Dustin Pedroia isn't sure how it happened, but once again, he's dealing with soreness in his right thumb.

This time, Pedroia (left, photo by Matt Stone) believes the problem is in a different spot from the torn adductor muscle that sidelined him for six games last month. But he's being held out of the lineup for today's series finale here against the Athletics, and he will be checked out tomorrow when the Red Sox return to Boston.

"I don't know, man. It's pretty frustrating," Pedroia said. "It was fine during the game (last night), and then I was sore after the game and today I'm pretty sore. Maybe it's from when I dove for that ball in right field. I don't know what happened.