Golfers Jon Rahm and Bryson DeChambeau are out of the Tokyo Olympics after testing positive for Covid-19.
World number one Rahm was positive in the final testing protocol before leaving for Japan.
DeChambeau, winner of the 2020 US Open, was also yet to travel to Japan. Both were set to make their Olympic debuts.
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The 27-year-old world number six has been replaced by Patrick Reed in the US team that also includes Justin Thomas, Collin Morikawa and Xander Schauffele.
"I am deeply disappointed not to be able to compete in the Olympics for Team USA," DeChambeau said in a USA Golf statement.
"Representing my country means the world to me and it was a tremendous honour to make this team. I wish Team USA the best of luck next week in Tokyo.
I will now focus on getting healthy, and I look forward to returning to competition once I am cleared to do so.
Reed said: "I am so excited to have the opportunity to represent our country and be a part of Team USA in Tokyo.
"I wish Bryson nothing but the best, and I know how disappointed he is to not be able to compete, and I will do my best to play my best and represent our country."
Andy Levinson, USA Golf executive director, said: "We're obviously disappointed for Bryson, as we know how much he was looking forward to representing the United States in his first Olympics.
"But we're thrilled that Patrick Reed is excited to play for his country when he is called upon, even with the strenuous testing protocols and he is set to arrive just in time to compete – on a golf course he will have never seen prior to the start of competition.
"It really illustrates the importance of the Olympics and the value Patrick places on playing for Team USA and for his country.
"We're excited to welcome him to Tokyo soon and know he'll be a formidable competitor for Team USA."
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