United States' Jessica Pegula celebrates after defeating Ukraine's Elina Svitolina in their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 15, 2021.(AP Photo/Andy Brownbill)

Ukraine's Elina Svitolina hits a backhand return to United States' Jessica Pegula during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 15, 2021.(AP Photo/Andy Brownbill)

United States' Jessica Pegula celebrates after defeating Ukraine's Elina Svitolina in their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 15, 2021.(AP Photo/Andy Brownbill)

Russia's Daniil Medvedev hits a backhand to United States' Mackenzie McDonald during their fourth round match at the Australian Open tennis championships in Melbourne, Australia, Monday, Feb. 15, 2021. (AP Photo/Hamish Blair)

United States' Jennifer Brady reacts during her fourth round match against Croatia's Donna Vekic at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 15, 2021.(AP Photo/Andy Brownbill)

Croatia's Donna Vekic is treated by a trainer during a break in her fourth round match against United States' Jennifer Brady at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 15, 2021.(AP Photo/Andy Brownbill)