Indiana Pacers star Paul George suffered an apparently severe lower right leg injury on Friday in a United States intra-squad scrimmage in preparation for the Basketball World Cup.
The injury was bad enough that the exhibition at the Thomas and Mack Center was immediately halted and George was quickly hospitalized.
George landed and his leg buckled horribly near the basket stanchion after he had fouled James Harden on a drive early in the fourth quarter.
Harden immediately doubled over in shock upon seeing the injury to his US team-mate and medical personnel, US coach Mike Krzyzewski and members of George's family attending the game moved to comfort the stricken player.
"With the serious injury that we had and the fact that we stopped playing for a long period of time, and out of respect for Paul and his family, the scrimmage is done," Krzyzewski told the crowd.
USA Basketball chairman Jerry Colangelo did not immediately confirm the exact nature of the injury, but just said the organization's only concern at the moment was for the player.
"This is a very tough blow," a grim-faced Colangelo said at a news conference. "It's a first for us in USA basketball to have something like this take place.
"It's a tough situation for our entire organization, our coaches and players are very, very emotional. There's no way the game could have gone on under the circumstances."
Colangelo said decisions about the final US selection for the Basketball World Cup, to be held in Spain on August 30-September 14, would take a back seat to making sure George was cared for properly.
"Our first concern, our primary concern, is Paul George," he said. "I want to reach out to the Indiana Pacers organization. I have a call into owner Herb Simon. This is a tough blow, not only for USA Basketball but for the Indiana Pacers.
"And so, as an organization, we're just going to let a little bit of time go by here before we address rosters or any of that stuff. It seems unimportant."
George, 24, has been an All-Star each of the last two years. The small forward averaged 21.7 points, 6.8 rebounds and 3.5 assists in 80 games last season for the Pacers, who lost to Miami in the Eastern Conference finals.