MELBOURNE, Australia (AFP) — Novak Djokovic smashed his racquet to bits and then swept Alexander Zverev out of the Australian Open as the defending champion followed Serena Williams and Naomi Osaka into the semi-finals yesterday.

It was a patchy performance from the world number one, who is nursing an abdominal injury and drew deeply on his mental fortitude to win 6-7 (6/8), 6-2, 6-4, 7-6 (8/6).

Djokovic will be hot favourite to reach Sunday’s final when he plays Russian qualifier Aslan Karatsev, who continued his dream run with a 2-6, 6-4, 6-1, 6-2 win against injured Bulgarian Grigor Dimitrov.

After destroying his racquet as he slipped behind in the third, Djokovic recovered brilliantly to take the set and he was ice-cool on the big points, drilling an ace to seal the decisive tiebreaker.

“Down to the very last shot it was anybody’s match,” said the 33-year-old Serb.

“A lot of nerves out there, a lot of pressure. Emotionally I feel a little bit drained, honestly.”

The Serb remains on track for a record-extending ninth Australian Open title and 18th Grand Slam trophy, nipping at the heels of rivals Roger Federer and Rafael Nadal, who both have 20.

Earlier, Williams took a step towards a record-equalling 24th Grand Slam title with a 6-3, 6-3 dismantling of second seed Simona Halep, her nemesis in the 2019 Wimbledon final.

Williams, 39, said her level was improving ahead of her meeting with Japan’s Osaka, who came out on top in their tempestuous 2018 US Open title match.

“Definitely think this is the best match I have played this tournament, for sure,” said the 10th seed.

“Obviously I had to, going up against the number two in the world, so I knew I had to do better.”

‘Intense’ Osaka

Their semi-final promises much after Osaka, the reigning US Open champion, looked in formidable touch in her 6-2, 6-2 win over Taiwan’s Hsieh Su-wei.

Displaying great focus against the awkward Hsieh, ranked 71 and playing her first Slam quarter-final aged 35, Osaka hit 24 winners and was detained on Rod Laver Arena for only 66 minutes.

“I told myself just to be really intense from the beginning,” said the Japanese star, the reigning US Open champion.

Elsewhere, 114th-ranked Karatsev became the first man to reach an Open-era Grand Slam semi on debut when he ousted a hobbling Dimitrov 2-6, 6-4, 6-1, 6-2.

The 27-year-old has knocked out three seeds as he became the lowest-ranked player to reach a major semi-final after world number 125 Goran Ivanisevic at Wimbledon in 2001.

“It’s an unbelievable feeling,” said Karatsev, whose career so far has been badly compromised by injury.

After a five-setter with Felix Auger-Aliassime in round four, Karatsev had an easier ride against Dimitrov who was wincing with pain from the third set.

The Bulgarian 18th seed, who was barely able to serve because of back spasms, took a medical time-out, but his movement was always hampered and he limped off the court after Karatsev’s win.

Karatsev becomes only the second qualifier to reach the Australian Open semi-finals after Bob Giltinan in 1977.

He was one of three Russians to reach the quarter-finals, with Daniil Medvedev and Andrey Rublev set to play each other today.