United States' Lauren Davis falls during ther third round match against Romania's Simona Halep at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)
Romania's Simona Halep celebrates after defeating United States' Lauren Davis in their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Ng Han Guan)
Romania's Simona Halep celebrates after defeating United States' Lauren Davis in their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)
United States' Madison Keys makes a backhand return to Romania's Ana Bogdan during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Dita Alangkara)
Romania's Ana Bogdan makes backhand return to United States' Madison Keys during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Dita Alangkara)
United States' Tennys Sandgren celebrates after defeating Germany's Maximilian Marterer during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Ng Han Guan)
South Korea's Chung Hyeon celebrates after defeating Germany's Alexander Zverev in their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)
Germany's Alexander Zverev breaks his racket in frustration during his third round match against South Korea's Chung Hyeon at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)
Germany's Angelique Kerber hits a backhand return to Russia's Maria Sharapova during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)
Russia's Maria Sharapova makes a backhand return to Germany's Angelique Kerber during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)
Switzerland's Roger Federer makes forehand return to France's Richard Gasquet during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)
Serbia's Novak Djokovic celebrates after defeating Spain's Albert Ramos-Vinolas in their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Dita Alangkara)
