Red Sox 1B Kevin Youkilis placed in 15-day DL with thumb injury, Mike Lowell activated

The Boston Red Sox put first baseman Kevin Youkilis on the 15-day disabled list with a thumb injury Tuesday and acknowledged that his season could be over.

Youkilis tore a muscle in his right thumb during Monday night's 6-5 loss to Cleveland. He lined out to end the first inning, grabbed his hand in pain and stayed in the game until the third.

"It's a very unusual injury — not a common occurrence for hitters to have this," Red Sox general manager Theo Epstein said. "It's not clear how long it'll be or it's not clear if he'll need surgery. If he does need surgery, it can be fixed."

Epstein said the injured muscle is one that helps move the thumb. Asked if surgery would end Youkilis' season, Epstein said: "Realistically, yes."

To take Youkilis' place on the roster, the club activated Mike Lowell from the 15-day disabled list. He has been hampered by a strained right hip.

Lowell, the MVP of Boston's 2007 World Series title, is batting .213 while getting just 80 at-bats this season. He was expected to start at first base on Tuesday.

Youkilis' injury is just another is a string that has hurt Boston this season. Leadoff hitter Jacoby Ellsbury has played nine games and been out since May 28 with fractured ribs. The 2008 AL MVP Dustin Pedroia is still trying to return from a broken left foot suffered in late June. He's been hitting, taking grounders and doing some running.

Backup catcher Jason Varitek is still out with broken right foot and starting catcher Victor Martinez missed 22 games after breaking the tip of left thumb, but returned just over a week ago. Center fielder Mike Cameron recently returned to the DL.

Starting pitchers Josh Beckett, Daisuke Matsuzaka and Clay Buchholz also missed time on the DL, but they are all back in the rotation now.

But the loss of Youkilis may be one of the biggest. He has switched between third and fourth in the order this season, batting .307 with 19 homers and 62 RBIs.

"It hurts, especially with Jacoby coming back, hopefully, the next day or two," Epstein said. "That's nothing new with this group this year."

Just a few days ago, Lowell expected to be traded at the deadline. When that didn't happen, he felt there was a chance he could be released. Now, he's needed with the loss of Youkilis.

"I don't think my emotions can go through any more roller coaster," he said. "I was told to wait until the 31st. Once the 31st came and went I was obviously frustrated."

Boston is in third place in the AL East behind New York and Tampa Bay. Manager Terry Francona said the team just needs to worry about winning games.

"That's the only way we know how to handle it," he said.