United States' Venus Williams celebrates after winning a point against Belgium's Kirsten Flipkens during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Rick Rycroft)

Canada's Denis Shapovalov smiles after winning a point against Italy's Jannik Sinner during the first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021. (AP Photo/Rick Rycroft)

Italy's Jannik Sinner makes a backhand return to Canada's Denis Shapovalov during the first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Rick Rycroft)

Bulgarian fans cheer Bulgaria's Tsvetana Pironkova during her first round match against Taiwan's Hsieh Su-Wei at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Andy Brownbill)

Serbia's Novak Djokovic makes a forehand return to France's Jeremy Chardy during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Rick Rycroft)

Romania's Simona Halep makes a forehand return to Australia's Lizette Cabrera during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Rick Rycroft)

Germany's Alexander Zverev smashes his racket in frustration during his first round match against United States' Marcos Giron at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Rick Rycroft)

France's Gael Monfils, right, congratulates Finland's Emil Ruusuvuori after their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Andy Brownbill)

United States' Serena Williams runs to return a shot to Germany's Laura Siegemund during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Rick Rycroft)

Japan's Naomi Osaka makes a backhand return to Russia's Anastasia Pavlyuchenkova during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021.(AP Photo/Rick Rycroft)