Australian player Nick Kyrgios says his country's handling of Novak Djokovic's visa dispute has been "really bad" and urged officials to "do better".
The men's world number one, 34, is facing deportation after his entry to the country was denied on Wednesday.
"This is one of our great champions but at the end of the day, he is human," said Kyrgios.
Djokovic has launched an urgent court challenge to be heard on Monday, a week before the Australian Open begins.
Australia requires all foreign visitors entering the country to be double vaccinated. Otherwise, they need to complete 14 days in quarantine.