Australian Open champion Novak Djokovic came through a tough examination of his fitness as the top seed beat Canadian powerhouse Milos Raonic 7-6 (7-4), 4-6, 6-1, 6-4 on Sunday to reach the quarter finals.

Djokovic, who injured a side muscle during a five-set win over Taylor Fritz on Friday and suggested he might not be able to continue, showed hints of discomfort on the way to becoming only the second player to reach 300 Grand Slam match wins.

Raonic, seeded 14th, had never taken a set off Djokovic in three previous Grand Slam meetings. So when he snatched the second set, it seemed an upset was possible.

But Djokovic, bidding for a record-extending ninth title in Melbourne, responded by raising his level and improving his record over Raonic to 12-0.

The Serb will face Germany’s Alexander Zverev for a place in the semi-finals. Zverev used his powerful serve to good effect to overcome 23rd seed Dusan Lajovic of Serbia 6-4, 7-6 (7-5), 6-3.

Third seed Dominic Thiem slumped out in lacklustre fashion, complaining of undisclosed physical issues after being thrashed 4-6, 4-6, 0-6 in the fourth round by Grigor Dimitrov.

Dimitrov will play Russian qualifier Aslan Karatsev next. Karatsev continued his fairytale run here, reaching the quarter finals on his Grand Slam debut with a 3-6, 1-6, 6-3, 6-3, 6-4 win over 20th seed Felix Auger-Aliassime.

Halep to meet Serena

Second seed Simona Halep survived an early wobble to beat Iga Swiatek 3-6, 6-1 6-4 as the Romanian avenged her shock defeat by the Polish teenager at the same stage of last year’s French Open.

Serena kept her bid for a record-equalling 24th Grand Slam singles title going with a hard-fought 6-4, 2-6, 6-4 win over Aryna Sabalenka.

Naomi Osaka saved two match points as she battled back from the brink to win 4-6, 6-4, 7-5 against Garbine Muguruza.

The Japanese third seed was chasing the match from the start and looked defeat square in the face in the third set when the Spanish 14th seed had two opportunities to win the match.

I dislike Djokovic: Kyrgios

Nick Kyrgios renewed his running feud with Novak Djokovic on Sunday when he mocked the world No. 1 with a grand entrance to an empty Margaret Court Arena for his doubles match.

Before a men’s doubles match with partner Thanasi Kokkinakis, the Australian imitated the way Djokovic celebrates victories with extravagant gestures.

“Just feeling the love,” the maverick Australian said. “Just trying to spread the good word of the celebration. Everyone loves that celebration. It’s well liked.”

Kokkinakis said there had been nothing malicious in the gestures. Kyrgios agreed, but could not resist directing another barb at Novak.

“We’re just having some fun,” he added. “Novak, I’m sure, doesn’t like me and we both have respect for each other, but I don’t like him at all, so it’s fun.”