Spanish tennist Rafael Nadal attends a press conference in Buenos Aires, Argentina, Feb. 23, 2015. Nadal will take part in the 2015 ATP Argentina Open tennis tournament starting on Tuesday. (Xinhua/Martin Zabala)

Spanish tennist Rafael Nadal attends a press conference in Buenos Aires, Argentina, Feb. 23, 2015. Nadal will take part in the 2015 ATP Argentina Open tennis tournament starting on Tuesday. (Xinhua/Martin Zabala)

Spanish tennist Rafael Nadal attends a press conference in Buenos Aires, Argentina, Feb. 23, 2015. Nadal will take part in the 2015 ATP Argentina Open tennis tournament starting on Tuesday. (Xinhua/Martin Zabala)

Spanish tennist Rafael Nadal attends a press conference in Buenos Aires, Argentina, Feb. 23, 2015. Nadal will take part in the 2015 ATP Argentina Open tennis tournament starting on Tuesday. (Xinhua/Martin Zabala)

Spanish tennist Rafael Nadal attends a press conference in Buenos Aires, Argentina, Feb. 23, 2015. Nadal will take part in the 2015 ATP Argentina Open tennis tournament starting on Tuesday. (Xinhua/Martin Zabala)