Top seed Novak Djokovic dropped a set for the first time at this year’s Australian Open but still reached the second week by beating Denis Shapovalov 6-3, 6-4, 4-6, 6-0.

The Serb is looking for a record seventh Aussie crown and he led 3-0 in the third set before wobbling against the 25th-seeded Canadian, one of the NextGen stars tipped to take over from the sport’s old guard.

Alexander Zverev kept his quest for a maiden Grand Slam on track with a comprehensive 6-3, 6-3, 6-2 win over Australian wildcard Alex Bolt on Rod Laver Arena.

The 21-year-old German number four seed and flagbearer for the next generation of young players cruised into the last 16 of the Australian Open for the first time in just 112 minutes.

Djokovic’s victory means he is guaranteed to stay world number one when the new rankings are released after the tournament. He next plays another young gun, Russia’s 15th seed Daniil Medvedev.

An irritated Djokovic lost his focus completely and dropped six of the next seven games after querying French umpire Damien Dumusois why the lights were on.

“I think there was no sense to turn on lights on court at 5pm when we have another four hours of daylight,” fumed the Serb 17-time Grand Slam winner.

“Did you guys see the balls well?,” he asked the crowd. “I saw them well too,” he said to a huge cheer. “Completely unnecessary to turn on the lights. The explanation I got was for TV reasons. I hope the viewers enjoyed it,” he added.

The normally mild-mannered Djokovic even received a code violation for verbally jousting with someone in the crowd who shouted “Nervous?”, as he faced three break points at 4-4, 0-40 in the third set.

Up till his mini-meltdown, Djokovic had made his outing on centre court look like an afternoon practice session for two-and-a-half sets against Shapovalov, one of the NextGen stars tipped to take over from the sport’s old guard

Kei Nishikori made it back-to-back victories for Japan on Saturday by sweeping into the fourth round after his compatriot Naomi Osaka managed the same earlier with a tough three-set win.

Nishikori, the in-form eighth seed, felt his way into the first set against Portugal’s 44th-ranked Joao Sousa before romping away to a 7-6 (8/6), 6-1, 6-2 win in 2hr 6min.

He was preceded onto Margaret Court Arena by countrywoman and US Open champion Osaka, who fought back from a set down to battle past Taiwan’s Hsieh Su-wei.

The 29-year-old Nishikori has won all three of his first week matches on the same Melbourne Park second showcourt to reach the last 16 of the Australian Open for the seventh time in nine appearances.

“I love to play this court, I’m very comfortable here,” said the 2014 US Open finalist after delighting a large contingent of Japanese fans. It’s great to play here, especially after Naomi today.”

Nishikori and Sousa had each survived two five-set epics before their third-round clash.

It looked odds-on for another marathon when they went shot-for-shot in the first set which Nishikori edged in a tiebreak after almost an hour.

But as the temperature began to rise in the mid-afternoon sunshine, he clearly decided he didn’t want to go the distance again.

He stepped hard on the accelerator, powering 19 unerring winners on his deadly forehand as he took just over an hour more to race through the second and third sets.

Former world number three Milos Raonic made short work of Frenchman Pierre-Hugues Herbert to reach the fourth round.

The 16th seed breezed through 6-4, 6-4, 7-6 (8/6) and will face fourth seed Alexander Zverev or Australian wildcard Alex Bolt next.

Raonic had needed four tiebreaks and four hours to see off former Australian Open champion Stan Wawrinka in round two, but the Canadian was in no mood to hang about on Saturday.

The big server, who reached the semi-finals in Melbourne in 2016, was never behind as he sped through the last-32 clash in just 121 minutes.

“I took yesterday off and didn’t come on to a tennis court, after four hours on one on Thursday,” said Raonic.

Rising star Daniil Medvedev cruised into the last 16 of a Grand Slam for the first time to set up a potential Australian Open showdown with Novak Djokovic.

The Russian 15th seed breezed past seasoned Belgium David Goffin 6-2, 7-6 (7/3), 6-3 in two hours on Melbourne Arena.

The 22-year-old Medvedev is fast becoming a force to be reckoned with, breaking into the world’s top 20 for the first time in October and reaching the final of the Brisbane International two weeks ago.

His breakthrough 2018 began in Australia 12 months ago when he won the Sydney International as a qualifier to lift his first ATP Tour title.

He pulled out of his title defence this year with a right shoulder problem but has had no issues in Melbourne, flying impressively into the second week without dropping a set.

Men’s singles - 3rd round

Daniil Medvedev (RUS x15) bt David Goffin (BEL x21) 6-2, 7-6 (7/3), 6-3

Kei Nishikori (JPN x8) bt Joao Sousa (POR) 7-6 (8/6), 6-1, 6-2

Pablo Carreno-Busta (ESP x23) bt Fabio Fognini (ITA x12) 6-2, 6-4, 2-6, 6-4

Milos Raonic (CAN x16) bt Pierre-Hugues Herbert (FRA) 6-4, 6-4, 7-6 (8/6)

(With AFP inputs)