Novak Djokovic said there were "a couple of things that had surfaced" fitness-wise after he beat Daniil Medvedev in the fourth round.
Pablo Carreno Busta and Alexander Zverev's frustration got the better of them as they suffered contrasting Australian Open exits.
With the world number one knocked out in Melbourne, four players are in contention to take over at the summit of the WTA rankings.
Novak Djokovic stayed on course to make history at Melbourne Park by getting past Daniil Medvedev in four sets.
The dramatic scenes at last year's US Open did not leave Patrick Mouratoglou fearful that he would lose his role as Serena Williams' coach.
Simona Halep took the positives from her Australian Open performance after Serena Williams knocked her out in the fourth round.
Australian Open quarter-finalist Stefanos Tsitsipas could join Marcos Baghdatis in having a souvlaki named in his honour in Melbourne.
Simona Halep pushed Serena Williams all the way in a gripping fourth-round contest, but the 23-time major champion came out on top.
Top seed Simona Halep pushed Serena Williams all the way, but the 23-time major singles champion moved into the last eight in Melbourne.
Alexander Zverev self-destructed in his straight-sets loss to Milos Raonic in the Australian Open last 16.
The 'Next Gen' are making a move at the Australian Open, with 10 men aged 22 or under reaching the third round.
American Amanda Anisimova, 17, broke records by upsetting Aryna Sabalenka 6-3 6-2 in Melbourne on Friday.
Stefanos Tsitsipas, 20, is relishing his upcoming battle with Swiss great Roger Federer in Melbourne.
Serena Williams, who is seeking an eighth Australian Open title, revelled in her 6-0 6-2 demolition of Tatjana Maria in Melbourne.
Maria Sharapova overpowered defending champion Caroline Wozniacki in the Australian Open third round.
Roger Federer overcame Dan Evans to move into the Australian Open third round.
Milos Raonic had to dig deep in a four-set victory over 2014 champion Stan Wawrinka at Melbourne Park.
Former world number one Andy Murray is leaning towards undergoing further surgery as retirement looms.
After downing Roger Federer, Stefanos Tsitsipas will not be content to rest on his laurels and is hoping to use the win as a springboard.
Sofia Kenin put up an excellent fight but could not finish the job against Simona Halep in the second round of the Australian Open.