Novak Djokovic has won 20 majors in his brilliant career, but he admits winning this U.S Open to complete the Grand Slam would be his crowning achievement.

That’s a significant statement, since a 2021 U.S. Open crown would also give Djokovic an all-time record 21 majors, one more than Roger Federer and Rafael Nadal, who are out with injuries.

The Grand Slam hasn’t been achieved since 1969, when Rod Laver captured all four majors in the same year. No male player had even won the first three, since Laver’s achievement 52 years ago, until Djokovic this year.

Djokovic has yet to talk to Laver before the U.S. Open, but hopes to. They usually chat during the Australian Open. According to a tennis source, Laver will be on hand for the U.S. Open, as he usually was before the pandemic.

“I’ll try to seek for his advice,’’ said Djokovic, who skipped all the hardcourt U.S. Open tune-ups because of the grind of playing at the Tokyo Olympics, in which he lost in the semifinals and the bronze-medal game. “Hopefully he can tell me something that could help me.’’

Djokovic has the Australian Open, French Open and Wimbledon all in the bag for 2021. Just seven more victories and history will be made in spades by the player known for his court coverage, stamina and resiliency more than any one stroke. 

“It would be [my best achievement],’’ Djokovic said. “I know how big of an opportunity is in front of me here in New York where historically I’ve played really well over the years. It’s probably the most entertaining tennis court we have. Crowds will be back on the stadium. I can’t wait. Honestly, I’m very motivated to play my best tennis. I will try to be in the moment, have a guiding star in a way, a dream to win the Slam here. I’m hugely inspired and motivated by that.’’

Federer, Nadal and defending champion Dominic Thiem have already withdrawn from the Open, but Djokovic is taking nothing for granted.

In fact, Russian Daniel Medvedev, the second seed who made the Open Finals in 2019, said, “Since I’m here, I want to say I’m going to try my best to keep [Djokovic] at 20 [majors] for all of them.

“We’re here to not let him win the U.S. Open.’’

Medvedev and Alexander Zverev, the tour’s hottest player, are Djokovic’s biggest roadblocks.

Djokovic could meet Zverev in the semifinals and could potentially face Medvedev in the finals. The big German used his serve to upset Djokovic in the Olympics and Zverev just captured the key Cincinnati warmup, from which Djokovic withdrew.

Then there’s the Greek factor, Stefanos Tsitsipas. None of the trio — Medvedev, Zverev and Tsitsipas — has won a major.

“My participation here, without Rafa and Roger participating, I feel it,’’ Djokovic said. “I know there’s a lot of people who are going to be watching my matches and expecting me to do well and fight for a [Grand] Slam. Regardless of Roger’s and Rafa’s absence, you still have tremendous quality tennis players that are probably right now on a hot streak, like Zverev, Medvedev, Tsitsipas, those are the three top contenders I see for the title. Anything can really happen.’’

Serena Williams, who also withdrew from this year’s tournament, is the last tennis player to enter the Open with a chance at a Grand Slam. She wasn’t successful in that 2017 attempt.

After knocking off clay-court master Nadal in the French Open semifinals, Djokovic was halfway to the Grand Slam after winning a five-set final over Tsitsipas. He knew it was possible then. Federer has won three majors in a year three times, but never the first three.

“I think Roland Garros is probably the one that is always probably the biggest hurdle for me,’’ Djokovic said. “ I won it the second time in my career this year. After I won the French, I thought, ‘OK, I don’t have a lot of time to prepare for Wimbledon, for grass, but I do feel more comfortable, and I like my chances more in Wimbledon than I probably do in Roland Garros.’ That probably would be identified as the moment where I felt it could be possible.’’

Djokovic’s last time on court was when he melted down against Pablo Carreno Busta in the bronze-medal Olympic match, throwing his racket into the stands, then smashing another one. It was eerily familiar because he melted down against Carreno Busta one year ago to cause his disqualification at the fan-less Open, when he accidently hit a linesperson with the ball.

Djokovic said his intentions were always to play last week’s Western & Southern Open in Cincinnati, but he didn’t have the energy. He arrived in New York on Sunday night.

“My preparations for US Open have gone well,’’ Djokovic said. “I feel good on the court. I took some time, little bit of an additional time off after Olympics. I just felt exhausted in every sense after that long summer, which was very successful. It brought a lot of success to me, a lot of confidence. Olympics, unfortunately (I) didn’t end up with a medal. It was a great experience of sharing the Village and the dining room with 10-plus-thousand athletes.’’

If Djokovic doesn’t pull off the Grand Slam, he’ll probably always regret going to Tokyo.