Reigning champion Novak Djokovic overcame some dips in form to beat Alexander Zverev 6-7(6) 6-2 6-4 7-6(6) and book his place in the Australian Open semi-finals on Tuesday.

The Serbian world number one hit back strongly after losing a tight opening set on a tiebreak but trailed in both the third and fourth sets before turning them around.

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2021? #AusOpen pic.twitter.com/YZ5MpuLVgy

— ATP Tour (@atptour) February 16, 2021

Germany’s Zverev will rue allowing Djokovic back from 4-1 down in the third set and he was also up 3-0 in the fourth.

Djokovic again wore tape on his abdominal area, a legacy of the injury picked up in his third-round win over Taylor Fritz. But it did not appear to bother him as he reached his 39th Grand Slam semi-final, where he will face an unlikely opponent in Russian qualifier Aslan Karatsev.

The 23-year-old Zverev began in confident fashion and secured the first break of the match but failed to convert a set point on Djokovic’s serve when leading 5-3.

He wavered on his own serve at 5-4 though, and Djokovic took the set into a tiebreak, only for some uncharacteristic errors to allow Zverev to sneak a 59-minute set.

Djokovic needed only 29 minutes to win the second set but his level dropped at the start of the third, and he destroyed a racket in anger as he slipped 4-1 behind.

Serving for a spot in the #AusOpen semifinals ????#AO2021 pic.twitter.com/lWrTm37mkl

— #AusOpen (@AustralianOpen) February 16, 2021

Zverev was 0-30 ahead on Djokovic’s serve in the next game but Djokovic found another gear, winning 20 of the next 24 points to move one set from victory.

Another momentum shift saw Zverev take a 3-0 lead in the fourth set and have three points to move 4-0 ahead, but Djokovic dug in to haul himself back into contention.

Zverev threatened to take the match into a decider but Djokovic saved a set point at 5-6 with an ace and a powerful first serve brought up match point in the day’s second tiebreak.

Djokovic netted a backhand but forced a volley error from Zverev to earn another chance, this time on his own serve, and he wrapped up the match with his 23rd ace.

QUALIFIER KARATSEV INTO MELBOURNE SEMIS

Qualifier Aslan Karatsev continued his stunning run into the Australian Open semi-finals on Tuesday, beating an ailing Grigor Dimitrov 2-6 6-4 6-1 6-2 to become the first man in the open era to reach the last four in his maiden Grand Slam.

The world number 114 was also only the fifth qualifier to reach the last four of a men’s major in the open era and the lowest-ranked player to reach a Grand Slam semi-final for two decades.

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— #AusOpen (@AustralianOpen) February 16, 2021

The Russian, whose success at getting into the Australian Open came on his 10th attempt to qualify for a Grand Slam, will meet eight-times champion Novak Djokovic for a place in the final.

“It’s an unbelievable feeling, first time main draw, first time semis,” said the 27-year-old, whose victory was marked only by canned applause with fans still banned from Melbourne Park because of a five-day coronavirus lockdown.

With Karatsev’s ATP Cup team mates Daniil Medvedev and Andrey Rublev facing off in a quarter-final on Wednesday, Russia are guaranteed to have two players in the semi-finals and could yet provide both finalists.

“I try not to think about it, I just look at the next match,” said Karatsev when asked about the prospect.