Beal, who was placed in the protocol Wednesday, was ruled out for the Summer Games on Thursday. It is unknown whether he tested positive for COVID-19 or is involved in contact tracing.
"I'm dying for [Beal]. We all are," Team USA men's basketball head coach Gregg Popovich said. "Since he was a little kid, this has been a dream of his, and he was playing great. ... For him and his immediate family, it's devastating. We just feel horrible about it."
USA Basketball later announced that Detroit Pistons forward Jerami Grant was placed in the protocol "out of an abundance of caution," though Popovich expressed optimism that he would be able to remain with the squad.
Popovich told reporters last week that three members of USA Select Team tested positive for COVID-19. The Select Team plays against the National Team at practices.
COVID-19 guidelines for Tokyo state that if athletes experience symptoms of COVID-19 in the 14 days before their arrival at the Summer Games, they should not travel to Japan and should inform a COVID-19 liaison officer and medical professional to determine the next steps.
Every Team USA athlete must submit two negative COVID-19 tests, from separate days, within 96 hours of departure for Tokyo.
Beal scored 17 points in 30 minutes in Team USA's 108-80 win over Argentina in an Olympic exhibition game Tuesday in Las Vegas. His replacement on the roster was not immediately revealed.
Team USA is scheduled to face Australia at 6 p.m. EDT Friday in Las Vegas, but that game could be in jeopardy of cancellation. ESPN reported that officials are in discussions about calling off the game due to the recent COVID-19 issues.
The Americans are set to battle Spain in their final scheduled exhibition game Sunday in Las Vegas. Team USA will meet France in its first game of the Tokyo Olympics at 8 a.m. EDT on July 25 in Saitama, Japan.