Novak Djokovic is No. 1 for a reason, says Alexander Zverev after semi-final loss

Novak Djokovic is "No. 1 in the world for a reason," Alexander Zverev said on Friday after going down in five sets to the Serbia national in the semi-final of the US Open.

Djokovic, who is aiming to win a record 21st Grand Slam, took three hours and 38 minutes to defeat the German player 4-6, 6-2, 6-4, 4-6, 6-2 at the Arthur Ashe Stadium.

"It was a great battle. Kind of a little bit disappointed with the start of the fifth set. To be honest, apart from that, it was a good match. I think we both left it all out there. The second break in the fifth set was so ridiculously unlucky that it sometimes happen. But he's No. 1 in the world for a reason and he showed that tonight," Zverev told ATP's official website after the match ended in New York on Friday.

Earlier this year, Zverev had stopped Djokovic from completing a Golden Slam by beating him in the last four clash of the Tokyo Olympics before eventually claiming the gold medal.

Following the gold medal win in Tokyo Games and a title win in Cincinnati, the 24-year-old Germany national was on a 16-match winning streak to the US Open semi-finals.

Zverev had dropped a set only once in the lead up to the match against Djokovic in New York – in the third round against Jack Sock – and came so close to becoming the first man since Djokovic in 2015-16 to reach consecutive US Open finals. Zverev, who won the 2018 World Tour Final, lost the US Open final to Dominic Thiem last year.

In the same post-match interview on Friday, Zverev insisted that eventually, it came down to Djokovic's mental toughness on the biggest points on Friday.

"He comes up with the best tennis when he needs to. We play 55-shot rallies. The only way for me to win that rally is to hit a forehand winner. That says it all, on a set point [down]. 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. There's a lot of reasons for that.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."

Nobody thought anybody will do it again, what Rod Laver did. To see him have the chance on Sunday - I do believe that he will do it - is great. He's breaking every single record that there is," added Zverev.

"If you look at the stats, if you look at the pure game of tennis action, he's the greatest of all time. Nobody is there with him, because most weeks World No. 1, most ATP Masters 1000 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?" the German star added further.

Djokovic will now face Russia's Daniil Medvedev in the final on Sunday. A win would mean, Djokovic, who is currently tied with legendary duo Rafael Nadal and Roger Federer (20 titles each), will surpass them in the list of most major titles.