Italy's Fabio Fognini reacts while playing against Australia's Alex De Minaur during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Feb. 13, 2021. (AP Photo/Hamish Blair)

Greece's Michail Pervolarakis makes a forehand return to Spain's Pablo Carreno Busta during their ATP Cup match in Melbourne, Australia, Friday, Feb. 5, 2021.(AP Photo/Hamish Blair)

Spain's Rafael Nadal waits for a serve from Britain's Cameron Norrie during their third round match a the Australian Open tennis championships in Melbourne, Australia, Saturday, Feb. 13, 2021. (AP Photo/Andy Brownbill)

Australia's Ash Barty hits a forehand return to Russia's Ekaterina Alexandrova during their third round match at the Australian Open tennis championship in Melbourne, Australia, Saturday, Feb. 13, 2021.(AP Photo/Andy Brownbill)

Russia's Andrey Rublev celebrates after defeating Spain's Feliciano Lopez in their third round match at the Australian Open tennis championship in Melbourne, Australia, Saturday, Feb. 13, 2021.(AP Photo/Andy Brownbill)

Greece's Stefanos Tsitsipas hits a forehand to Sweden's Mikael Ymer during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Feb. 13, 2021. (AP Photo/Hamish Blair)

Belgium's Elise Mertens serves to Switzerland's Belinda Bencic during their third round match at the Australian Open tennis championship in Melbourne, Australia, Saturday, Feb. 13, 2021.(AP Photo/Andy Brownbill)

Russia's Daniil Medvedev reacts during third round match against Serbia's Filip Krajinovic at the Australian Open tennis championship in Melbourne, Australia, Saturday, Feb. 13, 2021.(AP Photo/Andy Brownbill)

United States' Mackenzie McDonald hits a backhand return to South Africa's Lloyd Harris during their third round match at the Australian Open tennis championship in Melbourne, Australia, Saturday, Feb. 13, 2021.(AP Photo/Andy Brownbill)

United States' Jennifer Brady celebrates her win over Slovenia's Kaja Juvan during their match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Feb. 13, 2021. (AP Photo/Hamish Blair)

United States' Jessica Pegula hits a forehand to France's Kristina Mladenovic during their match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Feb. 13, 2021. (AP Photo/Hamish Blair)

Karolina Muchova of the Czech Republic and compatriot Karolina Pliskova play in an empty Rod Laver Arena during their third round match at the Australian Open tennis championship in Melbourne, Australia, Saturday, Feb. 13, 2021. The Australian Open continues but without crowds after the Victoria state government imposed a five-day lockdown starting Saturday in response to a COVID-19 outbreak at a quarantine hotel.(AP Photo/Andy Brownbill)