Switzerland

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Stan Wawrinka, of Switzerland, returns a shot from Horacio Zeballos, of Argentina, during a tennis match at the Miami Open, Saturday, March 25, 2017 in Key Biscayne, Fla. (AP Photo/Wilfredo Lee)

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Frances Tiafoe returns a shot from Roger Federer, of Switzerland, during a tennis match at the Miami Open, Saturday, March 25, 2017 in Key Biscayne, Fla. (AP Photo/Wilfredo Lee)

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Roger Federer, of Switzerland, tosses the ball to serve to Frances Tiafoe during a tennis match at the Miami Open, Saturday, March 25, 2017 in Key Biscayne, Fla. (AP Photo/Wilfredo Lee)

Roger Federer, of Switzerland, celebrates his 6-4, 7-5 win over Stan Wawrinka, of Switzerland, in the men's final of the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, poses with the trophy after his win against Stanislas Wawrinka, of Switzerland, in the finals of the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, poses with his trophy and the Swiss flag after defeating Stan Wawrinka, also of Switzerland, in their final match at the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, celebrates with the trophy after his win against Stanislas Wawrinka, of Switzerland, in the finals of the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Stan Wawrinka, of Switzerland, follows through on a return to Roger Federer, of Switzerland, during the men's final at the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Stan Wawrinka, of Switzerland, hits to Roger Federer, of Switzerland, during the men's final at the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, hits to Stan Wawrinka, of Switzerland, during the men's final at the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, celebrates his win against Stan Wawrinka, also of Switzerland, in their final match at the BNP Paribas Open tennis tournament, Sunday, March 19, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, right, hugs Jack Sock after his win a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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United States' Jack Sock hits to Roger Federer, of Switzerland, during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Jack Sock hits to Roger Federer, of Switzerland during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, hits to Jack Sock during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Roger Federer, of Switzerland, hits to Jack Sock during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Jack Sock hits to Roger Federer, of Switzerland, during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Pablo Carreno Busta, of Spain, hits to Stanislas Wawrinka, of Switzerland, during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Stanislas Wawrinka, of Switzerland, celebrates a point against Pablo Carreno Busta, of Spain, during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)

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Pablo Carreno Busta, of Spain, hits to Stanislas Wawrinka, of Switzerland, during a semifinal match at the BNP Paribas Open tennis tournament, Saturday, March 18, 2017, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)