Novak Djokovic is facing a race to be fit for his last-16 match against Milos Raonic on a day of intriguing match-ups at the Australian Open on Sunday.
Djokovic suffered an abdominal injury during his third-round win over Taylor Fritz and did not practise on Saturday.
"I don't know if I will step on court," the Serb said after Friday’s victory.
The world number one has been given the maximum time to recover as his match against Raonic is the final one on Rod Laver Arena on Sunday.
Eight-time Australian Open champion Djokovic needed courtside treatment against Fritz and later said he thought he had torn a muscle, adding: "I don't know if I will recover from that in two days.