Dimitrov's late surge as he searched in vain for only a second win over Djokovic in their 11th meeting will have left the Serbian wondering how much longer his injured hamstring will hold up as he prepares to take on 23-year-old Alex de Minaur.

Asked about younger rivals fourth seed Djokovic said: "What do you mean the young ones? Thirty five is the new 25, you know? Look at Rafa (Nadal), look at Andy Murray they're all playing at an extremely high level."

However, Murray’s run ground to a halt against Roberto Bautista Agut, the 24th-seeded Spaniard fending off the former world number one 6-1 6-7(7) 6-3 6-4.

"My feet didn't feel great. My legs were actually OK ... but I was struggling with my lower back," the 35-year-old Murray, who came through a five-set epic against Australian Thanasi Kokkinakis I the previous round, told reporters.

"That was affecting my serve and that was really the main thing today."

Australian De Minaur stepped out of Nick Kyrgios's shadow and ensured home fans will have someone to cheer in the second week as he steamrollered Frenchman Benjamin Bonzi 7-6(0) 6-2 6-1 in front of a heaving centre court crowd.

"To see a packed Rod Laver Arena was pretty special, you know, all having my back," the 22nd seed said. "It's one of those moments where you've just got to pinch yourself and stay in the moment."  

Double Delight  

Czech fans at Melbourne Park savoured double delight as 17-year-old Linda Fruhvirtova burst into the spotlight by joining former world number one Karolina Pliskova in the fourth round, while fifth seed Aryna Sabalenka continued her progress.

Sabalenka gave no quarter to former doubles partner Elise Mertens on Margaret Court Arena, beating the Belgian 26th seed 6-2 6-3 to continue her barnstorming start to the season.

The win set up an intriguing duel between the two players who won the season-opening tournaments in Adelaide, with Swiss 12th seed Belinda Bencic also through after beating Camila Giorgi 6-2 7-5 at Rod Laver Arena.

Sabalenka's emotions have often got the better of her but the big-hitting Belarusian said being "boring" was working for her.

"I need to be a little bit boring on court. I mean it's still about a lot of positive emotions for me, but I'm trying to stay away from negative and just fight for every point."

Men's fifth seed Andrey Rublev avoided a third round banana skin in the form of Dan Evans, the Russian sweeping aside the 25th seed 6-4 6-2 6-3 with 60 winners on a glorious afternoon.

A quarter-finalist two years ago, Rublev unleashed his wrath on the chair umpire in his previous match after being warned for an audible obscenity.

But it was all smooth sailing against Evans, who threw Rublev a banana during a change of ends at Margaret Court Arena when the Russian came up empty in his search for a snack.

"I didn't ask him (for one), I asked the ball-boy," said Rublev, who will meet Danish young gun Holger Rune for a place in the quarter-finals.

"He helped me with some energy, for sure."

Pliskova Resurgence

Pliskova, renowned for being a former world number one without a Grand Slam title, beat Russian Varvara Gracheva 6-4 6-2 in the early match at Rod Laver Arena to book a fourth round spot against China's Zhang Shuai.

Twice major finalist Pliskova missed last year's tournament after breaking her arm in a freak gym accident but victory over 23rd seed Zhang would continue the tall Czech's resurgence following her quarter-final run at Flushing Meadows.

Fruhvirtova, the youngest woman left in the singles, showed that the next generation of Czech tennis is in rude health as she rallied from a break down in the decider to beat compatriot Marketa Vondrousova 7-5 2-6 6-3.

She will next meet Croatian Donna Vekic, a 6-2 6-2 winner over Spain's Nuria Parrizas Diaz.

Olympic champion Bencic has now racked up nine straight wins, including the Adelaide International '2' title, in a near-perfect start to the season, a few months after linking up with Briton Emma Raducanu's former coach Dmitry Tursunov.

The United States will have four men in the last 16, with JJ Wolf and Tommy Paul beating fellow Americans Michael Mmoh and Jenson Brooksby, a day after Sebastian Korda downed twice finalist Daniil Medvedev.

Ben Shelton joined his compatriots by putting on a masterclass in powerhouse hitting to defeat local favourite Alexei Popyrin 6-3 7-6(4) 6-4.

Men's ninth seed Rune, one of the game's most exciting young talents, had a nasty fall against Ugo Humbert at John Cain Arena but after a lengthy medical time-out, the 19-year-old completed an impressive 6-4 6-2 7-6(5) win over the Frenchman.