Tennys Sandgren said it was unfair on players forced to stay in their hotel rooms for 14 days after Covid-19 cases on their charter flights to Australia.
Roger Federer saved seven match points to come from two sets down and beat Tennys Sandgren for a place in the Australian Open semi-finals.
Fabio Fognini was beaten by US world number 94 Tennys Sandgren 6-3, 7-6 (12/10), 6-3 on the compact Court 14.