BOSTON -- After making a nifty diving stop and nailing Pudge Rodriguez to open Wednesday's game against the Tigers, third baseman Mike Lowell wiggled his left hand with a look of discomfort on his face.

As it turns out, Lowell sprained his left thumb and had to be removed from the game in the bottom of the second inning. X-rays proved to be negative, much to the relief of Lowell and the Sox.

Still, Lowell was wearing a splint after the game and wasn't sure when he'd be able to play again. It's all but certain that he will miss Thursday's series finale against the Tigers.

"It's throbbing a little. I'd really prefer not to try to move it," said Lowell. "I can't move it with any force."

Lowell has been a quick healer in the past, and he is hopeful that this injury won't keep him out for anything longer than a couple of days.

"I would definitely not want to go on the disabled list," he said.

Last June, Lowell sustained a similar injury against the Yankees and missed the next night's game. But he later admitted he might have come back too soon, as the injury lingered for about a week.

"That's where tomorrow, I think, is going to be a day where it lets me know a lot, so I'm kind of hoping for the best," he said.

At first, Lowell was hoping this injury was nothing. But between innings, he tried to swing off a tee, and he couldn't muster much of anything. In the top of the second inning, he fielded a ground ball and immediately felt the pain. He came out of the game between innings.

Sean Casey pinch-hit for Lowell and promptly stung a single up the middle to start what proved to be a two-run rally.

Casey stayed in the game and played first base, and Kevin Youkilis moved across the diamond to third. The Red Sox will probably stick with that alignment for as long as Lowell is out.

"For him to come out of a game, you know it's hurting," said manager Terry Francona. "We're never going to do something we think is going to adversely effect somebody. He was already examined today, he'll be examined again tomorrow and hopefully we'll know a lot more on how he shows up."