Estonian Kaia Kanepi caused the biggest shock of the day by knocking out defending women's champion Sofia Kenin ©Getty Images

Picture Gallery

Greece's Stefanos Tsitsipas celebrates after overcoming Australian wildcard Thanasi Kokkinakis in five sets ©Getty Images
Greece's Stefanos Tsitsipas celebrates after overcoming Australian wildcard Thanasi Kokkinakis in five sets ©Getty Images
Australia's big hope Ashleigh Barty continued her smooth progress by defeating compatriot Daria Gavrilova ©Getty Images
Australia's big hope Ashleigh Barty continued her smooth progress by defeating compatriot Daria Gavrilova ©Getty Images
Russian fourth seed Daniil Medvedev was another straight sets winner in the second round in Melbourne ©Getty Images
Russian fourth seed Daniil Medvedev was another straight sets winner in the second round in Melbourne ©Getty Images
Sofia Kenin was the biggest casualty on day four, with the defending women's singles champion losing in straight sets to Estonia's Kaia Kanepi ©Getty Images
Sofia Kenin was the biggest casualty on day four, with the defending women's singles champion losing in straight sets to Estonia's Kaia Kanepi ©Getty Images
Due to the coronavirus pandemic, spectators are only able to attend in limited numbers at this year's Australian Open ©Getty Images
Due to the coronavirus pandemic, spectators are only able to attend in limited numbers at this year's Australian Open ©Getty Images
Belinda Bencic, the 12th seed, was made to work hard by Svetlana Kuznetsova for her three set victory ©Getty Images
Belinda Bencic, the 12th seed, was made to work hard by Svetlana Kuznetsova for her three set victory ©Getty Images
Italians Fabio Fognini and Salvatore Caruso (in white) embrace at the net following their match, shortly before the pair got involved in a heated exchange ©Getty Images
Italians Fabio Fognini and Salvatore Caruso (in white) embrace at the net following their match, shortly before the pair got involved in a heated exchange ©Getty Images
Security staff removed a disruptive spectator from the Rod Laver Arena during Rafael Nadal's second round match ©Getty Images
Security staff removed a disruptive spectator from the Rod Laver Arena during Rafael Nadal's second round match ©Getty Images
Russian seventh seed Andrey Rublev battled through in three close sets against Brazil's Thiago Monteiro ©Getty Images
Russian seventh seed Andrey Rublev battled through in three close sets against Brazil's Thiago Monteiro ©Getty Images