Spain's Rafael Nadal signs autographs after defeating Damir Dzumhur of Bosnia and Herzegovina in their third round match at the Australian Open tennis championships in Melbourne, Australia, Friday, Jan. 19, 2018. (AP Photo/Vincent Thian)
Denmark's Caroline Wozniacki blows kisses to the crowd after defeating Slovakia's Magdalena Rybarikova in their fourth round match at the Australian Open tennis championships in Melbourne, Australia Sunday, Jan. 21, 2018. (AP Photo/Dita Alangkara)
Denmark's Caroline Wozniacki hits a forehand return to Slovakia's Magdalena Rybarikova during their fourth round match at the Australian Open tennis championships in Melbourne, Australia Sunday, Jan. 21, 2018. (AP Photo/Dita Alangkara)
Spain's Carla Suarez Navarro celebrates after defeating Anett Kontaveit of Estonia in their fourth round match at the Australian Open tennis championships in Melbourne, Australia Sunday, Jan. 21, 2018. (AP Photo/Dita Alangkara)
Spain's Carla Suarez Navarro, right, shakes hands with Anett Kontaveit of Estonia after she won their fourth round match at the Australian Open tennis championships in Melbourne, Australia Sunday, Jan. 21, 2018. (AP Photo/Dita Alangkara)
Croatia's Marin Cilic celebrates after defeating Spain's Pablo Carreno Busta in their fourth round match at the Australian Open tennis championships in Melbourne, Australia Sunday, Jan. 21, 2018. (AP Photo/Ng Han Guan)
Belgium's Elise Mertens makes a forehand return to Croatia's Petra Martic during their fourth round match at the Australian Open tennis championships in Melbourne, Australia Sunday, Jan. 21, 2018. (AP Photo/Andy Brownbill)
