Lee Westwood said on Thursday that new U.S. Open champion Tiger Woods had done well to conceal the level of pain he was playing under when he clinched his 14th major title this week.

Westwood, the world number 17, played Sunday's final round at Torrey Pines alongside Woods, and only missed a place in Monday's playoff with the world number one and Rocco Mediate when he missed a 20-foot birdie putt at the 72nd hole.

Woods announced on Wednesday that he would be having reconstructive surgery on his left knee that would rule him out for the rest of the year.

He underwent surgery in April to clean out the cartilage but grimaced in pain on numerous shots during his victory in San Diego.

"He played in pain but he did a very good job of hiding it. It was obviously worse than we all thought," Westwood told BBC Sport.

"Obviously it's always disappointing every time he's not playing, when you win with him it means much more.

"But they will not put a mark next to your name in the book (when you win a tournament) and say this one doesn't mean as much because Tiger wasn't there."

Woods will miss the final two majors of the year, the British Open and the US PGA Championship, as well as September's Ryder Cup clash against Europe in Kentucky.

Westwood was buoyant ahead of his home major at Royal Birkdale next month.

"They are offering 20-1 on me now, it's come in since last week's 100-1. I'm optimistic and I'm looking forward to recreating last week's form."