A general view of Melbourne Park as tennis players undergo a mandatory quarantine ahead of the Australian Open in Melbourne, Australia January 21, 2021. REUTERS/Kelly Defina

Tennis player Alexander Bublik of Kazakhstan arrives to a training at Melbourne Park as players undergo mandatory quarantine in advance of the Australian Open in Melbourne, Australia January 21, 2021. REUTERS/Kelly Defina

Tennis player Alexander Bublik of Kazakhstan arrives to a training at Melbourne Park as players undergo mandatory quarantine in advance of the Australian Open in Melbourne, Australia January 21, 2021. REUTERS/Kelly Defina

A general view of Melbourne Park as tennis players undergo a mandatory quarantine ahead of the Australian Open in Melbourne, Australia January 21, 2021. REUTERS/Kelly Defina

Tennis players and staff undergoing mandatory quarantine ahead of the Australian Open arrive for training in a restricted area at Melbourne Park in Melbourne, Australia January 21, 2021. REUTERS/Kelly Defina

Tennis player Coco Gauff of the United States is seen training at Melbourne Park as players undergo mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

A staff member wearing PPE works to clean surfaces at Melbourne Park in between training sessions for tennis players undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

A staff member wearing PPE works to clean surfaces at Melbourne Park in between training sessions for tennis players undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis player Coco Gauff of the United States is seen training at Melbourne Park as players undergo mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis player Coco Gauff of the United States is seen training at Melbourne Park as players undergo mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis player Coco Gauff of the United States is seen training at Melbourne Park as players undergo mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

A tennis player practices with a racket inside a room at a hotel where players are undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

A tennis player practices with a racket inside a room at a hotel where players are undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis player Sabrina Santamaria heads from accommodations where players are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis player Sabrina Santamaria heads from accommodations where players are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis players are escorted from accommodations where they are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis player Joran Vliegen heads from accommodations where players are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis players are escorted from accommodations where they are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis players and support staff are escorted from accommodations where they are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis player Jonny O'Mara heads from accommodations where players are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

Tennis players and support staff are escorted from accommodations where they are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 21, 2021. REUTERS/Kelly Defina

A tennis player undergoing mandatory quarantine ahead of the Australian Open trains in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A general view of Australian Open signage in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players undergoing mandatory quarantine ahead of the Australian Open leave a restricted training area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A healthcare worker assists tennis players undergoing mandatory quarantine ahead of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A worker sanitizes a fence at the Australian Open training grounds in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players undergoing mandatory quarantine ahead of the Australian Open train in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A general view of Australian Open flags in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A sign is seen at the entrance to the Australian Open training grounds in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players undergoing mandatory quarantine ahead of the Australian Open train in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A sign prohibiting public access is seen at the entrance to the Australian Open training grounds in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A tennis player undergoing mandatory quarantine ahead of the Australian Open trains in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players undergoing mandatory quarantine ahead of the Australian Open train in a restricted area in front of their accommodation in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players undergoing mandatory quarantine ahead of the Australian Open train in a restricted area in front of their accommodation in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A tennis player undergoing mandatory quarantine ahead of the Australian Open trains in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A tennis player undergoing mandatory quarantine ahead of the Australian Open train in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players undergoing mandatory quarantine ahead of the Australian Open train in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Healthcare workers wearing personal protective equipment approach quarantined tennis players training in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A tennis player undergoing mandatory quarantine ahead of the Australian Open trains in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A tennis player undergoing mandatory quarantine ahead of the Australian Open trains in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Healthcare workers wearing personal protective equipment speak to quarantined tennis players training in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players undergoing mandatory quarantine ahead of the Australian Open train in a restricted area in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A woman is escorted from accommodations where tennis players and support staff are undergoing mandatory quarantine to a nearby training facility in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Police officers patrol outside accommodations where tennis players are undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A tennis player undergoing mandatory quarantine enters a restricted training area in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A tennis player undergoing mandatory quarantine enters a restricted training area in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis players and support staff walk from accommodations where they are undergoing mandatory quarantine to train at a nearby facility in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A man looks out of a window of accommodations where tennis players and support staff are undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Paramedics load a man into an ambulance outside accommodations where tennis players and support staff are undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Paramedics load a man into an ambulance outside accommodations where tennis players and support staff are undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis coach Rohan Fisher is escorted from accommodations where players and support staff are undergoing mandatory quarantine to a nearby training facility in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A woman is escorted from accommodations where tennis players and support staff are undergoing mandatory quarantine to a nearby training facility in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

A paramedic arrives at accommodations where tennis players and support staff are undergoing mandatory quarantine in advance of the Australian Open in Melbourne, Australia, January 20, 2021. REUTERS/Sandra Sanders

Tennis - ATP Finals - The O2, London, Britain - November 22, 2020 Russia's Daniil Medvedev embraces Austria's Dominic Thiem after he wins their final match Action Images via Reuters/Paul Childs

Tennis - ATP Finals - The O2, London, Britain - November 22, 2020 Russia's Daniil Medvedev lifts the trophy as he celebrates winning the final match against Austria's Dominic Thiem Action Images via Reuters/Paul Childs

Tennis - ATP Finals - The O2, London, Britain - November 22, 2020 Russia's Daniil Medvedev with the trophy after winning the final match against Austria's Dominic Thiem REUTERS/Toby Melville

Tennis - ATP Finals - The O2, London, Britain - November 22, 2020 Russia's Daniil Medvedev celebrates with the trophy after winning the final match against Austria's Dominic Thiem Action Images via Reuters/Paul Childs

Tennis - ATP Finals - The O2, London, Britain - November 22, 2020 Russia's Daniil Medvedev lifts the trophy as he celebrates winning the final match against Austria's Dominic Thiem Action Images via Reuters/Paul Childs

Tennis - ATP Finals - The O2, London, Britain - November 22, 2020 Russia's Daniil Medvedev lifts the trophy as he celebrates winning the final match against Austria's Dominic Thiem Action Images via Reuters/Paul Childs

Tennis - ATP Finals - The O2, London, Britain - November 22, 2020 Russia's Daniil Medvedev kisses the trophy as he celebrates winning the final match against Austria's Dominic Thiem Action Images via Reuters/Paul Childs