Novak Djokovic dropped his first set of the Australian Open but recovered to beat Denis Shapovalov and ensured he will remain world number one at the end of the tournament.
Shapovalov, 19, is one of the stars of the next generation and the Canadian had his moments on Rod Laver Arena, not least winning five games in a row from 1-4 to win the third set.
But Djokovic responded emphatically to win 6-3 6-4 4-6 6-0 and set up a last-16 clash with another talented young player in Russia's Daniil Medvedev.
Djokovic appeared to lose his concentration after complaining to the umpire when the floodlights were turned on during the third set.
"I think there was no sense to turn on the lights on the court at 5pm when we have another four hours of daylight," he said.
"I thought it was completely unnecessary. The explanation we got was it was for TV reasons. I hope the viewers enjoyed it."
Japan's Kei Nishikori moved swiftly into the fourth round after beating Joao Sousa of Portugal 7-6(6) 6-1 6-2.
The comfortable victory came as a relief to the eighth seed and former U.S. Open finalist after he battled through consecutive five-set matches in the opening rounds.
"I think today will help," the three-times quarter-finalist said after setting up a clash with Spain's 23rd seed Pablo Carreno Busta.
Both Nishikori and Sousa entered their match after tight opening rounds and were evenly matched in the early exchanges on their favoured hard court surfaces.
But after a close tiebreaker, Nishikori took near total control, increasing the pace on his ground strokes and showing soft hands at the net; a quality his opponent couldn't replicate.
He said he would continue attacking the net after using the tactic successfully on Saturday.
"I think third set, I started coming (in) a little more, I think that was working well," said Nishikori.
Fourth seed Alexander Zverev avoided any more drama with a 6-3 6-3 6-2 victory against Australian wild card Alex Bolt.
After going five sets against Jeremy Chardy in the last round, Zverev would have wanted to conserve some energy and he emerged unscathed to set up a last-16 clash with in-form Milos Raonic.
