Flushing Meadows, New York, USA; Danil Medvedev of Russia serves the ball against Frances Tiafo of the United States on day eight of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York,USA; Alexander Zverev of Germany serves against Borna Coric of Croatia (not pictured) in a men's singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Sep 6, 2020; Flushing Meadows, New York, USA; Novak Djokovic of Serbia and a tournament official tend to a linesperson who was struck with a ball by Djokovic against Pablo Carreno Busta of Spain (not pictured) on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Novak Djokovic of Serbia and a tournament official tend to a linesperson who was struck with a ball by Djokovic against Pablo Carreno Busta of Spain (not pictured) on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Naomi Osaka of Japan hits a forehand against Marta Kostyuk of Ukraine (not pictured) on day five of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Serena Williams of the United States serves against Maria Sakkari of Greece (not pictured) on day eight of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. (Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Naomi Osaka of Japan serves the ball against Anett Kontaveit of Estonia on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York,USA; Serena Williams of the United States hits a forehand against Tsvetana Pironkova of Bulgaria (not pictured) in a women's singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York,USA; Yulia Putintseva of Kazakhstan reaches for a forehand against Jennifer Brady of the United States (not pictured) in a women's singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Serena Williams of the United States hits a backhand against Maria Sakkari of Greece (not pictured) on day eight of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. (Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Naomi Osaka of Japan returns the ball against Shelby Rogers of the United States in the women?s singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York, USA; Pablo Carreno Busta of Spain celebrates winning the fifth set and match against Denis Shapovalov of Canada in the men s singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York, USA; Naomi Osaka of Japan hits balls into the stands after her win against Anett Kontaveit of Estonia on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York, USA; Maria Sakkari of Greece serves against Amanda Anisimova of the United States (not pictured) on day six of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Serena Williams of the United States walks onto the court prior to her match against Maria Sakkari of Greece (not pictured) on day eight of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. (Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Novak Djokovic of Serbia discusses with a tournament official after being defaulted for striking a lines person with a ball against Pablo Carreno Busta of Spain (not pictured) on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York,USA; Serena Williams of the United States reacts after winning a point against Tsvetana Pironkova of Bulgaria (not pictured) in a women's singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Roberto Bautista Agut of Spain reaches for a volley against Vasek Pospisil of Canada (not pictured) on day six of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Felix Auger-Aliassime of Canada hits the ball against Dominic Thiem of Austria on day eight of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Denis Shapovalov of Canada hits the ball against David Goffin of Belgium on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York, USA; Serena Williams of the United States celebrates after match point against Maria Sakkari of Greece (not pictured) on day eight of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. (Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Naomi Osaka of Japan wearing a George Floyd mask hits balls into the stands after her win against Shelby Rogers of the United States in the women?s singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York,USA; Serena Williams of the United States serves against Tsvetana Pironkova of Bulgaria (not pictured) in a women's singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Shelby Rogers of the United States serves the ball against Naomi Osaka of Japan in the women?s singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

Flushing Meadows, New York, USA; Petra Martic of Croatia hits a backhand against Yulia Putintseva of Kazakhstan (not pictured) on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Danielle Parhizkaran-USA TODAY Sports

Flushing Meadows, New York, USA; Denis Shapovalov of Canada slips as he return the ball against Pablo Carreno Busta of Spain in the men s singles quarter-finals match on day nine of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports