The Australian Open rolls on amid a Melbourne lockdown, but the tournament risks losing its greatest champion in the first week as fans wait to hear if Novak Djokovic will be fit to play on Sunday.

Djokovic suffered a muscle tear in his third-round five-set epic against Taylor Fritz, and the world No. 1 skipped practice on Saturday in a bid to recover in time to resume his quest for a record-extending ninth title at Melbourne Park.

Withdrawing from the tournament would be devastating for the defending champion who has won 17 Grand Slams in all, especially after his fourth-round disqualification in the US Open last year when he accidentally hit a ball at a line judge.

His next opponent, Canadian Milos Raonic, may not complain, however, having lost all 11 times he has played Djokovic.

Rafa advances

Rafael Nadal extended his winning streak against fellow left-handers to 18 with a 7-5, 6-2, 7-5 victory over Cameron Norrie that earned him a place in the fourth round.

Daniil Medvedev finally worked out how to a win a five-setter. All by himself.

The fourth-seeded Medvedev was 0-6 in career five-setters, and his match against No. 28-seeded Filip Krajinovic looked like it was going all the way .

“My coach (Gilles Cervara) said he’s sure I’m going to win the match,” Medvedev explained after 6-3, 6-3, 4-6, 3-6, 6-0 win.

In the women’s section, top-ranked Australian Ash Barty beat Ekaterina Alexandrova of Russia 6-2, 6-4 to reach the fourth round .

Karolina Muchova, the 25th seed Czech, staged an astounding comeback in the second set to beat No. 6 Karolina Pliskova 7-5, 7-5.