Los Angeles Clippers forward Blake Griffin will miss the London Olympics after suffering a torn meniscus in his left knee, Clippers coach Vinny Del Negro said.
Griffin, who was sent from the US team's training camp in Las Vegas to Los Angeles for tests, is to undergo arthroscopic surgery to repair the damage.
"Missing out on the Olympic experience will be tough for him to take. I know how dedicated he was to doing that. We're glad we can get this fixed now and take advantage of the available time for him to fully recover," Del Negro said.
The move adds another major injury setback to an American squad of NBA stars already hurt by injuries to Orlando center Dwight Howard, Miami stars Chris Bosh and Dwyane Wade and Chicago's 2011 NBA Most Valuable Player Derrick Rose.
Anthony Davis, the college star who was selected by New Orleans with the first overall pick in last month's NBA Draft, was called back to the US Olympic training camp after having been cut last weekend and named a US team alternate.
Griffin, who had originally injured the knee in the first round of the NBA playoffs, appaently aggravated it on Wednesday in a practice session.
The US squad was already struggling with a lack of height before the injury to Griffin, one of its taller playmakers, who averaged 20.7 points and 10.9 rebounds a game last season.
Griffin, the top pick in the 2009 NBA Draft, signed a five-year NBA contract extension with the Clippers on Tuesday night that could be worth as much as $95 million.
Griffin also missed what should have been his rookie season in the NBA with a serious knee injury. He was last year's NBA Rookie of the Year with 22.5 points and 12.1 rebounds a game.
Davis, a teen star who helped the University of Kentucky win the US college crown this year, suffered a left ankle injury during his first workout for the Hornets after the draft but is now healthy and ready to play for the Americans.
Davis was picked with an eye to a possible change in Olympic basketball to a 23-and-under event, much the way Olympic football is staged. Davis would be 23 at the time of the 2016 Rio de Janeiro Olympics and a likely US team leader.
The US lineup includes Miami star LeBron James, Los Angeles Lakers playmaker Kobe Bryant, NBA scoring champion Kevin Durant and his Oklahoma City teammates Russell Westbrook and James Harden, and Chris Paul of the Clippers.
But the loss of Howard and Bosh left Tyson Chandler of Chicago as the US team's only true center, and losing Griffin will add to the size problem, which US coach Mike Krzyzewski says will be eased by versatility and athleticism.
The Americans will spend the next three days training in Washington before another exhibition game against Brazil.