CNN  — 

Novak Djokovic is one win away from a record-breaking 21st major title and the first calendar grand slam in men’s singles since 1969.

He needed the full five sets to do it, but the world No. 1 from Serbia defeated No. 4 Alexander Zverev of Germany 4-6, 6-2, 6-4, 4-6, 6-2 in the US Open semifinal at Arthur Ashe Stadium on Friday.

Djokovic, 34, is tied with Roger Federer and Rafael Nadal with 20 major singles titles – the most in men’s tennis. He will face Russian and world No. 2 Daniil Medvedev in the final on Sunday.

On the court after Friday’s win, Djokovic said: “There’s only one match left. All in, let’s do it. I’m going to put my heart and my soul and my body and my head into that one. I’m going to treat the next match like it is the last match of my career.”

The last man to complete the calendar grand slam – winning the Australian Open, French Open, Wimbledon and US Open in the same year – was Rod Laver in 1969. Laver tweeted a picture of himself watching Friday’s semifinal, saying “Great to be back in New York, watching the history channel.”

Six years ago, Serena Williams attempted to complete a calendar grand slam, which hadn’t been done on the women’s circuit since Steffi Graf in 1988. Graf also won gold in singles at the Olympics that year, making her the only tennis player – male or female – to complete a so-called golden slam, winning Olympic gold in addition to all four majors.

Williams went on to be shocked in the US Open semifinals by Roberta Vinci.

In the early hours Saturday, Djokovic referenced Williams’ run, saying: “I remember I won 2015, I won that year’s US Open. I was talking to Serena. She was very emotional about everything that was going on. I can relate to what she’s been going through right now. I understand it now. Obviously, once you’re in that situation, you can really comprehend what a player goes through.”

Djokovic said he understands why Williams wanted to avoid questions about her loss, and spoke of the pressure top players feel to keep winning.

“At the end of the day, you have to go out on the court and deliver. You’re expected to always win. For a great legend that she is, she always has that expectations from everyone, including herself,” he said. “It’s no different with me.”

In his post-match press conference, Zverev said of Djokovic: “If you look at the stats, if you look the pure game of tennis action, he’s the greatest of all time.

“There is a reason why he’s won 20 grand slams. There’s a reason why he’s spent the most weeks at world No. 1… I think mentally he’s the best player to ever play the game. Mentally in the most important moments, I would rather play against anybody else but him.”

Djokovic plays Medvedev on Sunday. The 25-year-old defeated 12th seed Felix Auger-Aliassime of Canada in straight sets earlier Friday, reaching his third grand slam final. He has dropped just one set in this year’s US Open.

This will be Medvedev’s second US Open final, having lost to Nadal in five sets in 2019. He lost the Australian Open final to Djokovic in straight sets earlier this year.

After his semifinal win, Medvedev said he learned a lot from that match against Djokovic in Melbourne.

“He was playing different than the matches he did before me, and I was kind of not ready for it. So now I am,” Medvedev said of Djokovic’s tactics.

Of the final, he said: “It’s going to be more interesting in terms of tactic what I’m going to prepare .. No matter the score, I’m just going to turn up the heat, if I can say, and try to do my best, even more than what I did in Melbourne.”

At the Tokyo Olympics this summer, Djokovic – who had already won the Australian Open, French Open and Wimbledon – had the opportunity to go for the golden slam.

Instead, he left without a medal after losing to Zverev in the semifinals. It was Zverev, a finalist at last year’s US Open, who went on to win the gold medal in the best-of-three-sets format.