USA's Frances Tiafoe returns the ball to Switzerland's Stan Wawrinka during their Mexico ATP Open 500 men's singles tennis match in Acapulco, Guerrero State, Mexico on Feb 24, 2020. (PHOTO / AFP)

Frances Tiafoe will be unable to compete for the Washington Kastles in the 2020 World TeamTennis season after testing positive for COVID-19 during the advance travel testing window, tournament chief Carlos Silva said on Monday.

World TeamTennis, an innovative mixed-gender professional tennis league, will start from July 12 at the Greenbrier, West Virginia, and up to 500 fans will be allowed to attend matches

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Tiafoe, 22, returned a positive test on Friday and was forced to withdraw from the All-American Team Cup exhibition tournament in Atlanta.

World TeamTennis, an innovative mixed-gender professional tennis league, will start from July 12 at the Greenbrier, West Virginia, and up to 500 fans will be allowed to attend matches.

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Grand Slam champions Venus Williams, Kim Clijsters and Sofia Kenin are among the players who have signed up for the three-week event featuring nine mixed-gender teams in action.