Roger Federer admits he needed "a bit of luck" to beat John Millman

"I think John played a great match. It came down to the wire, a bit of luck maybe. I had to stay so focused, take the right decisions. He kept on coming up with the goods.

"I thought, 'OK, I didn't play too bad'. I was getting ready to explain myself in the press conference. What a match. John deserved over half of this one."

Having seen Serena Williams and Naomi Osaka lose on Rod Laver Arena before him, it would have been understandable had Federer felt a few extra nerves, particularly given Millman had been the opponent for one of the most uncomfortable nights of his life.

That came a year and a half ago at the US Open, when the likeable Queenslander knocked out Federer in extreme heat and humidity.

Conditions were very different in Melbourne but there was plenty more discomfort for the 38-year-old, who struggled to find his timing and was a break down in the deciding set.

This was the biggest match so far to be decided by the first-to-10-point tie-break introduced last year, and it was an extraordinary denouement.

Federer made 82 unforced errors, 48 of them off the forehand, but this was a night where his competitive resilience was the biggest weapon in his armoury as he kept alive his hopes of winning a 21st grand slam title.

If he is to have a chance of doing that, he will need to play a lot better, starting against Hungary's Marton Fucsovics in two days' time.

Federer came unstuck in the fourth round 12 months ago against Stefanos Tsitsipas, but the Greek was the hunted this year as he tumbled out 7-5 6-4 7-6 (2) to Milos Raonic.

The big-serving Canadian Raonic has endured wretched luck with injuries over the last few years but was in supreme form.

Tsitsipas had never faced the Raonic serve in the a match before, and he said: "It's one shot that you can get knocked down all the time, and you're just there, getting punched in the face with one shot.

"I felt a bit stupid returning his serves. I felt like I was slow. My anticipation was not there. It's a strange game of tennis in general."

Raonic will next face 2018 finalist Marin Cilic, who is unseeded this year but enjoying a fine tournament, with his latest victory coming in five sets over Roberto Bautista Agut.

There were no problems, though, for defending champion Novak Djokovic, who produced a serving masterclass to defeat Yoshihito Nishioka 6-3 6-2 6-2.

The second seed hit 17 aces and lost just eight points on serve during the match, seven of them in the third set.

Djokovic, who has former Wimbledon champion Goran Ivanisevic among his team, said: "I love playing on the court. I like the conditions. I'm starting to feel very, very comfortable and compact on the court. I'm going to try to keep that going."

In the fourth round, Djokovic will face 14th seed Diego Schwartzman, who beat Dusan Lajovic 6-2 6-3 7-6 (7).

Fucsovics continued his fine tournament with a 6-1 6-1 6-4 victory over Tommy Paul while Tennys Sandgren, who reached the quarter-finals two years ago, defeated fellow American Sam Querrey 6-4 6-4 6-4.

Next up for Sandgren will be a rematch with 12th seed Fabio Fognini, who was a straight-sets winner over Guido Pella.

Sandgren defeated Fognini at Wimbledon last summer, with the Italian apologising after being overheard saying he wished a bomb would explode at the All England Club.