Novak Djokovic survived the biggest test so far in his bid for the calendar grand slam by coming from a set down against Matteo Berrettini to reach the US Open semi-finals.

The world No 1 has been a cut above the rest of the field in 2021 and is looking to complete the set with the title in New York, having already lifted the Australian Open, French Open and Wimbleton titles.

In a rematch of the Wimbleton final a few months ago, there was a sense of deja vu when Djokovic dropped the opening set to big-serving sixth seed Berrettini.

But in the end, just as at Wimbleton, Djokovic struck back to win in four, triumphing 5-7, 6-2, 6-2, 6-3 in three hours and 26 minutes.

The Serbian’s task does not get any easier, though, as his semi-final opponent is Alexander Zverev, the man who denied him a shot at the golden slam by beating him at the Tokyo Olympics.

Djokovic said on court following his latest win: ‚He’s in tremendous form, he’s been winning a lot. He has comfortably moved to the semi-finals here.

‚I know his game well, we played in Tokyo. He’s one of the best players in the world, but the bigger the challenge the more glory in overcoming it.

‚This was a great match, with a lot of energy on and off the court. Matteo is a terrific player and every time we face each other it’s a close battle.

‚When I lost the first set I managed to forget about it and move on. I was locked in at the start of the second and it was the best three sets I’ve played so far.‘

It was a 26th consecutive victory at a major for Djokovic and came on the 52nd anniversary of Rod Laver becoming the last man to win all four grand slam events in the same year.

But it was far from plain sailing in a brutal 77-minute first set in which both players put each other’s serve under intense scrutiny.