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

BBC reported that seven-time winner Serbian Star  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.

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 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.

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.

“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 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.