Champ Djokovic through to Open round four

Novak Djokovic is in to his 13th fourth round at the Australian Open.
Novak Djokovic is in to his 13th fourth round at the Australian Open.

A serving masterclass has put Novak Djokovic's rivals on notice as the Serb declared his delivery the best it could be after a third round Australian Open demolition of Yoshihito Nishioka.

The No.2 seed breezed through the clash, registering a 6-3 6-2 6-2 win over the Japanese in just one hour and 25 minutes.

The reigning Australian Open champion set up a round of 16 encounter with Diego Schwartzman, who he rated amongst the fastest players on tour.

But being quick and doing something with Djokovic's serve are two very different things as the equally fleet-footed Nishioka discovered on Friday.

Djokovic served 17 aces and gave away just one point on serve in the first two sets of the match.

It left the seven-time Melbourne Park winner pondering when he'd last served as well.

"That's probably as best as my serve can actually be at the moment, which I'm very pleased with," he said.

"It allows me to go quicker through my games and win more dominantly my service games and put additional pressure on the service games of my opponents. That's definitely something that's useful going towards the second week of the grand slam."

Earlier, Schwartzman had enjoyed a 6-2 6-3 7-6 (9-7) win over Djokovic's countryman, Dusan Lajovic.

The match against the Argentine will mark Djokovic's 50th in the fourth round at a major and 13th in Melbourne.

There was another big-serving exhibition on Margaret Court Arena as 2016 semi-finalist Milos Raonic upset sixth seed Stefanos Tsitsipas 7-5 6-4 7-6 (7-2).

The 32nd seed dropped 19 aces to leave Tsitsipas and his Greek fans stunned.

He'll take on marathon man Marin Cilic for a spot in the quarter-finals after the Croat pulled off another five-set win, downing Roberto Bautista Agut 6-7 (3-7) 6-4 6-0 5-7 6-3.

After losing the first set Cilic picked apart one of the form players on tour, at one stage going on an 11-game winning run from 3-4 down in the second to 2-0 up in the fourth.

Bautista Agut, who'd won eight straight matches to start the year including not dropping a set at the ATP Cup, won just five points in the second set.

Known for his resilience, the Spaniard rode out the storm however, stealing a break back and capturing another to take the match into a decider before the 2018 finalist triumphed.

"I had that incredible patch, that surreal level I was hitting every single ball and it was going in," said Cilic who won his round two match against Benoit Paire in a super tiebreaker.

"But I knew Roberto was going to fight, he is always a great fighter and competitor."

Tennys Sandgren, a 2018 quarter-finalist, also moved through to the last 16 with a straight sets win over fellow American Sam Querrey while Marton Fucsovics downed Tommy Paul and Fabio Fognini beat Guido Pella.

Australian Associated Press