World number one Novak Djokovic is a match away from one of the highest achievements across sports, with a calendar Grand Slam on the line after he overcame German Alexander Zverev 4-6 6-2 6-4 4-6 6-2 in the U.S. Open semi-final in New York on Friday (September 10).

Djokovic moved within one win of reaching a men’s record 21 Grand Slam titles and avenged his loss to Zverev at the Tokyo Olympics in front of a roaring crowd inside Arthur Ashe Stadium, with Rod Laver sitting in the front row, 52 years after he achieved the feat, the last man to do so.

He will face Russian Daniil Medvedev in Sunday’s (September 12) final, after the world number two sent off 21-year-old Canadian Felix Auger-Aliassime in his semi-final.

Djokovic handed the German his first break of the night with a double fault in the first set but otherwise showed no mercy, firing off 41 winners and a dozen aces across the entire match.

The third set was a matter of survival of the fittest. Djokovic had a 40-0 head start in the tenth game only to see Zverev fend off two break points through marathon rallies, including a 53-shot exchange, before he broke the German’s serve for the set point.

Tied at two sets apiece, Djokovic won a 30-shot rally for the early break, but after fending off four break points saw Zverev convert in the seventh game. He broke Zverev’s serve in the next game before hoisting his arms aloft to wild cheers from the crowd.

“Yeah, I mean it’s a great win,” said Djokovic in his news conference. “I’m proud of the fight that I delivered. Yeah, I probably could have played better in some moments but again, I have to be satisfied with delivering the best tennis I possibly could in the most important set, which was the fifth set.”

Zverev was tipped to be the toughest test at the U.S. Open for the Serbian. Not only had he ended Djokovic’s bid for a Golden Slam – the four majors and the Olympic gold in the same year – six weeks back, the German was also on a career-best 16-match winning streak before Friday’s contest.

“One thing that was very good from him is how he served on breakpoints,” Zverev added. “Most of the time I didn’t have a chance. That was the big difference tonight.

“I feel like every time it was an important moment, he came out with massive serves.”

Currently in a three-way tie for most men’s tennis major titles at 20 a piece with Roger Federer and Rafa Nadal, with whom he makes up tennis’ “Big Three,” Djokovic could also exceed his rivals in the sheer number of Grand Slam trophies if he wins on Sunday.

Both Federer and Nadal missed the year’s final major due to injury.

“I know we want to talk about history. I know it’s on the line. I’m aware of it. Of course, I’m aware of it.

“But I’m just trying to lock into what I know works for me. So I have my routines, I have my people. I isolate myself. I gather all the necessary energy for the next battle, only the next match, the next match.

“I said it on the court. I’m going to treat this match as it’s my last one because it’s arguably the most important one of my career maybe. Maybe not, I don’t know. But of this year, for sure.

“I’ll be giving it all I’ve possibly got in the tank to win this match.”

While tennis fans the world over enjoy endless debate over who of tennis’ “Big Three” can truly lay claim to the title “Greatest of All Time,” for Zverev, the matter was already settled.

“If you look at the stats, if you look at the pure game of tennis, he’s the greatest of all time,” said Zverev. “Nobody is there with him, because most weeks world No. 1, most Masters 1000s titles, most likely going to be the most Grand Slams at the end of the day.

“And he has the chance of winning all four in the same year. How do you compete with that?”