Australian Open: Novak Djokovic to face Milos Raonic in quarter-finals

Defending champion Novak Djokovic reached his 11th Australian Open quarter-final with a 6-3 6-4 6-4 win over Argentine Diego Schwartzman.

The seven-time winner was frustrated with himself in the opening set but broke the 14th seed in the eighth game.

Schwartzman fought back after losing the first three games of the second set but could not halt the resurgent Serb.

Djokovic broke again in the fifth game of the third set en route to victory in Melbourne.

The world number two will have to raise his level against his next opponent, Milos Raonic, who secured a 6-4 6-3 7-5 over 2018 finalist Marin Cilic.

Tennys Sandgren came through a feisty match against Fabio Fognini to set up a quarter-final meeting with six-time champion Roger Federer.

American Sandgren beat the Italian 12th seed 7-6 (7-5) 7-5 6-7 (2-7) 6-4 in a match that saw Fognini given a point penalty for unsportsmanlike conduct.

Fognini was given the penalty for taking off his shirt between games, which is only permitted at a change of ends.

The 32-year-old then refused to play until he had received medical attention for a blister on his finger, which left Sandgren visibly annoyed.

Sandgren was later forced to take a medical time-out for treatment on his heavily strapped right knee.

"It's a rollercoaster sometimes with [Fognini]. Sometimes you're just a passenger with what's going on," Sandgren said.

"He doesn't play well, all of a sudden he's playing amazing, you're stuck with your hands in your pockets like, 'Shoot, I'd like to play tennis, too'."

Despite the straight-set win, this display was not as impressive as the one produced against Yoshihito Nishioka in the previous round. The opening games of the first set were a struggle as Djokovic muttered to himself over his form.

He improved as the set wore on though, and looked at his best in the first few games of the second before Schwartzman broke his opponent for the only time.

However, the Serb regained control of the match and eventually sealed victory in just over two hours.

"This will be a different match-up to he one today," said Djokjovic. "Raonic is one of tallest and strongest players. He's also got one of biggest serves. I'm ready for missiles.

"One of the key elements will be how well I'm returning. It's good to see Milos healthy. He's a great guy and good friend."

Canadian Raonic, seeded 32nd, dominated the Croat throughout with almost double the number of winners - 55 to 29 - and 35 aces compared to Cilic's five.

Unseeded Cilic did have two set points when leading 5-4 in the third set but Raonic saved them and then broke his opponent in the next game before serving out the win.