Japan's Naomi Osaka in action during the Australian Open match in Second Round against China's Saisai Zheng at Melbourne Park, Melbourne, Australia, January 22, 2020. Defending champion Naomi Osaka struggled on serve and produced one of the most animated tantrums of the tournament so far before fending off China's Zheng Saisai to reach the third round of the Australian Open on Wednesday. REUTERS/Kai Pfaffenbach

Japan's Naomi Osaka in action during the Australian Open match in Second Round against China's Saisai Zheng at Melbourne Park, Melbourne, Australia, January 22, 2020. After being broken early in the second set, Japan's Osaka threw her racket, slammed a ball into the court and gave her racket a kick for good measure before steadying the ship and earning a 6-2 6-4 win at Margaret Court Arena. REUTERS/Hannah Mckay

Japan's Naomi Osaka in action during the Australian Open match in Second Round against China's Saisai Zheng at Melbourne Park, Melbourne, Australia, January 22, 2020. Defending champion Naomi Osaka struggled on serve and produced one of the most animated tantrums of the tournament so far before fending off China's Zheng Saisai to reach the third round of the Australian Open on Wednesday. REUTERS/Kai Pfaffenbach

Japan's Naomi Osaka in action during the Australian Open match in Second Round against China's Saisai Zheng at Melbourne Park, Melbourne, Australia, January 22, 2020. After being broken early in the second set, Japan's Osaka threw her racket, slammed a ball into the court and gave her racket a kick for good measure before steadying the ship and earning a 6-2 6-4 win at Margaret Court Arena. REUTERS/Kai Pfaffenbach

Japan's Naomi Osaka in action during the Australian Open match in Second Round against China's Saisai Zheng at Melbourne Park, Melbourne, Australia, January 22, 2020. Defending champion Naomi Osaka struggled on serve and produced one of the most animated tantrums of the tournament so far before fending off China's Zheng Saisai to reach the third round of the Australian Open on Wednesday. REUTERS/Kai Pfaffenbach

Japan's Naomi Osaka signs autographs for fans after winning the Australian Open match in Second Round against China's Saisai Zheng at Melbourne Park, Melbourne, Australia, January 22, 2020. After being broken early in the second set, Japan's Osaka threw her racket, slammed a ball into the court and gave her racket a kick for good measure before steadying the ship and earning a 6-2 6-4 win at Margaret Court Arena. REUTERS/Hannah Mckay