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)

Russia's Andrey Rublev prepares to serve to Norway's Casper Ruud during their fourth round match at the Australian Open tennis championships in Melbourne, Australia, Monday, Feb. 15, 2021. (AP Photo/Hamish Blair)

Spain's Rafael Nadal hits a backhand return to Italy's Fabio Fognini during 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)

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)

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)

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