He dropped a set for the first time this year against fast-rising Canadian Denis Shapovalov, before demolishing him in the fourth stanza to win 6-3, 6-4, 4-6, 6-0, AFP reported.
"I just tried to be in the moment and weather the storm," said the Serb, who was unsettled when the lights were switched on in Rod Laver Arena for television reasons, despite it still being daylight.
"Completely unnecessary to turn on the lights," he said in roasting the organizers.
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 up-and-coming star, Russia's 15th seed Daniil Medvedev.
Another young gun Alexander Zverev made the last 16 for the first time when he swatted aside Australian Alex Bolt in three sets and will play former world number three Milos Raonic for a place in the quarterfinals.
Medvedev enjoyed a rush of confidence after securing his first appearance in the last 16 of a Grand Slam and the Russian tyro hopes to ride it to an unlikely victory over Djokovic.
The 22-year-old Muscovite crushed former world number seven David Goffin 6-2, 7-6(3), 6-3 of Belgium at Melbourne Arena and now heads into the biggest match of his career feeling he is playing with house money, Reuters reported.
Like many of his generation, Medvedev grew up watching Djokovic battling ‘Big Four’ rivals for Grand Slam trophies and has huge respect for the Serb’s record and reputation.
Yet he also believes the 31-year-old is not quite the player he was, even as the world number one bids for a third major title in succession.
“...what I can only say is that probably he is not playing as he was before,” the Russian told reporters.
“Or that’s just (my) feeling. Because before, when he was young, I was just watching on TV but it was just something insane when he was playing Andy (Murray) or somebody for five hours and you couldn’t see one down (level), it was only up.
“It’s not the same right now, you always have chances to beat him.
“That’s why he lost three times to ‘Next Gen’ players last year and I’m going to try to find my chances.”
Medvedev may study Zverev’s upset win over the Serb at the season-ending World Tour Finals, or seek inspiration from compatriot Karen Khachanov who downed Djokovic at the Paris Masters in a major upset.
Medvedev has played him twice, losing in straight sets at Eastbourne in 2017 but took a set off the 14-time Grand Slam champion before retiring during a Davis Cup tie the same year.
“I don’t know if he was in a worse moment (at the time),” Medvedev said.
“I managed to give him some fight, even if I lost two times. I’ve improved a lot since then.
“I think what is good about Novak is he gives you time.
“It’s not like Roger (Federer) who takes the ball early, or like (Milos) Raonic when you know you’re going to run like crazy for all the match.
“Of course, he’s a great player but at least you can build your game, this gives you some chances.”
World number one Simona Halep set up a headline last 16 showdown with Serena Williams by beating her sister Venus Saturday.
The Romanian finally hit form to pull off her best win of the year and cruise past the veteran American 6-2, 6-3, AFP wrote.
"I was super-motivated today," she said after being taken to three sets in both her opening two matches as she bounces back from a herniated disc that ended her 2018 season early.
"I have nothing to lose," she added, looking ahead to Monday's clash against 23-time Grand Slam winner Serena. "I playing against a great champion. Its's going to a bigger challenge but I'm ready to face it."
Williams crushed Ukrainian Dayana Yastremska 6-2, 6-1 before consoling her at the net as the teenager burst into tears.
The ominous 37-year-old, seeded 16, has dropped just nine games in her three matches so far on her first return to the tournament since winning it in 2017 while pregnant.
"I just play each match at a time, play as hard as I can and do the best I can. That really is all you can do," she said as she zeroes in on an eighth Australian title and a record-equaling 24th Slam crown.