Ivo Karlović

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Nick Kyrgios, of Australia, reacts after winning a point against Ivo Karlovic during the Miami Open tennis tournament, Monday, March 27, 2017, in Key Biscayne, Fla. (AP Photo/Lynne Sladky)

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Steve Johnson, of the United States, returns the ball to Ivo Karlovic, of Croatia, at the Citi Open tennis tournament, Thursday, July 31, 2014, in Washington. (AP Photo/Luis M. Alvarez)

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South Africa's Kevin Anderson returns the ball to Croatia's Ivo Karlovic during their third round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Saturday, May 31, 2014. (AP Photo/Michel Euler)

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Croatia's Ivo Karlovic looks down as he plays South Africa's Kevin Anderson during their third round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Saturday, May 31, 2014. (AP Photo/Michel Euler)

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Croatia's Ivo Karlovic returns the ball to South Africa's Kevin Anderson during their third round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Saturday, May 31, 2014. (AP Photo/Michel Euler)

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Croatia's Ivo Karlovic clenches his fist after scoring a point during the first round match of the French Open tennis tournament against Bulgaria's Grigor Dimitrov at the Roland Garros stadium, in Paris, France, Tuesday, May 27, 2014. (AP Photo/Michel Spingler)