Carl Crawford will undergo season-ending Tommy John surgery on Thursday, the Red Sox announced on Monday night.

Crawford has what the team termed a "chronic" ulnar collateral tear in his left elbow. He is expected to miss nine months.

Crawford first suffered the injury during spring training when he was rehabbing from offseason wrist surgery.

He is in the second season of a seven-year, $142 million contract.

"We were trying to manage it conservatively and his symptoms increased over the last few days," general manager Ben Cherington said. "We talked more late last weekend and over the weekend, but Carl wanted to get through the weekend and play in the Yankee series and we agreed to circle up again (Monday) and we decided to get it taken care of."

"It became clear over the last few days that surgery was going to happen, it was just a question of when," Cherington added. "We felt, after talking with Carl, it was the right thing to do to get it taken care of now. To Carl's credit, he had played through the injury and played pretty well, but since it wasn't getting better and symptoms were getting worse, we decided it wasn't fair to keep asking him to go out there, so we decided to take care of it now and he agreed with that."