PORTLAND, Ore. (AP) -- Greg Oden has suffered yet another setback with his troublesome knees.

The often-injured 7-foot center was undergoing a minor procedure Monday to clear out debris in his left knee in Vail, Colo., when the surgeon determined there was additional damage and performed microfracture surgery, the Portland Trail Blazers said.

The former No.1 pick in the 2007 NBA draft has now had two microfracture surgeries on his left knee, and one on his right. He has also undergone surgery for a fractured left kneecap.

The Blazers say Oden will not play this season.

"It's hard to put into words the heartbreak for everyone involved, but especially for Greg. He's a young man who has experienced a great number of physical challenges in his playing career and today is yet another significant setback for him," Trail Blazers President Larry Miller said in a prepared statement. "We have a lot of empathy for Greg and his family during this difficult time."

Oden, who has not played in an NBA game since Dec. 5, 2009, has appeared in 82 career games for the Blazers, averaging 9.4 points and 7.3 rebounds.

It was expected that he might be able to play this season, but a checkup before the start of training camp in December reportedly revealed concerns about a non-weight-bearing ligament in the left knee, further setting back his rehabilitation.

Oden was a restricted free agent heading into this season. The Blazers and Oden initially agreed to an $8.9 million qualifying offer for this year, but when the setback was announced the two sides restructured the deal, which was dropped to $1.5 million. He will become an unrestricted free agent following this season.

Oden has turned down several interview requests this season.

Shortly after the news about the latest surgery broke, Blazers forward LaMarcus Aldridge posted on Twitter: "Praying for my bro G.O. get better!"

The Blazers were in Los Angeles on Monday night for a game against the Lakers.

"I'm sure he's saying, `Why Me?' Sometimes in life, things like that happen, and you wonder why it's happening to you," coach Nate McMillan said about Oden before the game. "Some of these injuries have occurred, not only on the floor but off the floor. There's really not an explanation for why, or sometimes how they're happening. I'm sure it's been a frustrating start for him."

Portland's acting general manager Chad Buchanan told reporters that the team knew there was the possibility of an additional microfracture surgery when he went in for the procedure. The doctor found two defects, he said.

Buchanan was asked whether the latest surgery might mean the end of Oden's career.

"Greg's still very young, in relative terms, for a professional basketball player. He's recovered from a couple of these before - his last two microfracture lesions have healed fine," Buchanan said. "So there's no reason to think he couldn't come back as long as he shows the work ethic and desire that he's had in the past to come back. I think it's premature to speculate anything beyond that."

The former Ohio State star was selected over Oklahoma City's Kevin Durant with the top pick in the 2007 draft. Debates raged over who should be the No. 1 selection, and the Blazers eventually went with Oden in the hope that he would lead the team - along with Brandon Roy and Aldridge - to an NBA championship.

But Oden's rookie season was postposed when he required microfracture surgery on his right knee that forced him to miss the 2007-08 season.

Oden's repeated knee problems have drawn comparisons to Sam Bowie, the injury-plagued big man the Blazers selected ahead of Michael Jordan in the 1984 draft. While Bowie played in 76 games his rookie season, averaging 10 points and 8.6 rebounds, he appeared in just 63 games over the next four seasons because of injuries. He missed the entire 1987-88 season. In all, he had five operations.

© 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Learn more about our Privacy Policy and Terms of Use.