Novak Djokovic will surpass Federer and Nadal, he is the 'best ever', Ivanisevic says

Goran Ivanisevic has no doubts that Novak Djokovic will create history at the 2021 US Open and claim the elusive calendar-year Grand Slam. The Croatian believes there is no one that can stop the Serb at the moment, after he claimed his third major of the year at Wimbledon on Sunday.

Djokovic joined "Big Three" rivals Roger Federer and Rafael Nadal on 20 men's singles Grand Slam titles, but Ivanisevic feels that he will overtake the duo in 2021. The 2001 Wimbledon champion, who is part of the Serb's coaching team, believes that Djokovic is now the greatest of them all having matched the feat.

"Everything is possible. I'm not going to say [he will reach] 30 [Grand Slams] because it's a long way. But five, six, seven years ago, we were talking about [Roger] Federer, only about Federer. Now you have [Rafael] Nadal and him competing [for] who is going to be the best ever," Ivanisevic said, as quoted on the ATP Tour website.

"For me, Novak is the best ever. He's writing history. He's going to do it [at the] US Open. I strongly believe he's going to do it, he's going to win all four in one year."

Djokovic will become just the second man in the Open Era to complete the calendar-year Grand Slam after Rod Laver achieved it in 1969. Ivanisevic admitted that it is an honour to be part of the world number one's team, and also explained why it is so difficult to beat the Serb at the moment.

"He's like in the movies. You have to kill the guy 27 times and still he gets up and you have to kill him again and he gets up, he gets up," Ivanisevic added. "This is great. I'm proud to be there and to witness that, to be part of that. [He] is going to make history, I strongly believe he will do it."

Djokovic admitted after his sixth Wimbledon title that he feels that he can win the US Open in two months' time and make history. The Serbian star can add the Olympic gold medal to his kitty to make it a "Golden Slam," but is still unsure about his participation at this month's summer games in Tokyo.