Bradley Beal will not represent the United States at this year's Olympic Games as he remains in health and safety protocols, while team-mate Jerami Grant is also now isolating.
USA Basketball (USAB) had announced on Wednesday that a player, widely reported to be Beal, had entered the protocols.
Thursday brought confirmation that the Washington Wizards guard would not be able to travel with the team to Tokyo. Team USA's opening game against France is just 10 days away.
"Bradley Beal, who was placed under USA Basketball's health & safety protocols on Wednesday, will remain in protocol and will be unable to participate in the Tokyo Olympic Games," a USAB statement read.
"Out of an abundance of caution, Jerami Grant has been placed under health and safety protocols."
Beal had started in all three Team USA exhibitions to date, concerning back-to-back losses to Nigeria and Australia followed by a win over Argentina.
The Wizards scorer led the team alongside Kevin Durant with 17 points against Argentina.
Beal's absence represents a blow to a team whose preparation has been far from ideal, their first consecutive exhibition defeats in the professional era coming as they still wait on NBA Finals trio Devin Booker, Khris Middleton and Jrue Holiday to join the roster.
Enough talent remains at Greg Popovich's disposal to ensure Team USA remain favourites to win a 16th gold medal in their 19th Games appearance, but Beal had been among the NBA's best this season on a middling Washington side.
Only Steph Curry averaged more than Beal's 31.3 points per game in the regular season.
Beal has steadily improved in this regard over the past four years, setting new career highs in three seasons in a row (25.6, 30.5, 31.3).
As he now resorts to the role of spectator as the United States tackle a group containing France, Iran and the Czech Republic, Beal is likely to again become the subject of trade rumours.
A high-performing player on a Wizards team with no serious title prospects, his future is far from certain.
Beal missed a free throw in the Argentina game as a fan shouted that Washington instead needed to "trade Russell Westbrook", his team-mate.