Novak Djokovic and Rafael Nadal both left New York yesterday, bound for Serbia and Spain respectively.

However, the world’s top two players, who fought out a gruelling, intense and, at times, almost unbelievable final at the US Open on Monday night, will have to wait for their well-earned rest.

Both men are due back in action for their countries in their respective semi-finals of the Davis Cup; Serbia at home to Argentina and Spain against France in Cordoba.

It is a mark of their commitment that they both say they will be available but after what they put themselves through in four spectacular sets of tennis here, few people would argue if they were to pull a sickie.

Djokovic, of course, will go home to a hero’s welcome -- for the third time this year -- after his 6-2, 6-4, 6-7, 6-1 victory gave him a first US Open title, his third grand slam title of 2011 and the fourth of his career.

Nadal will go home heartened by the way he fought back in the third set but still wondering how Djokovic has managed to turn the tables in the space of 12 months.

This time last year, it was Nadal who was celebrating his third major victory of 2010, top of the world after completing a career set of all four grand slam titles. Twelve months on, Djokovic has won the Australian Open, Wimbledon and the US Open, and lost just two of 66 matches played in 2011.

Some might think that there is only one way he can go from here but as he considered the latest achievement in what John McEnroe has called “the greatest year anyone has put together in tennis”, Djokovic seems hungry for more.

“There are still a lot of things to prove, to myself and to the tennis world,” the Serb said. “I still want to win many more events, many more major events. It’s the love for the sport that keeps me going and the feeling of winning on the court. As long as it stays with me, I will keep fighting for more trophies.

“It would be unbelievable to be able to complete the [career] grand slam, to win the French Open. It’s something that is definitely an ambition, but it’s going to take time.”

“I guess it takes some time to realise the success that I had this year, especially now, winning another major. It’s probably going to all settle down towards the end of the year when I take some time off and analyse it.”

Djokovic has beaten Nadal in six straight finals in 2011, on three different surfaces, including twice in grand slams. It is a phenomenal turnaround for a player who was once thought of as hugely talented but physically brittle.

Whether it is his gluten-free diet (a diet he planned to put on hold for one night of celebrations, including “a bunch of alcohol”) or his improved fitness routine, or his improved mental strength, something has clearly clicked.

But Djokovic said he believed it was down to a combination of hard work and the confidence that he has gained from winning close matches against the top players.

“It’s just that I’m hitting the shots that I maybe wasn’t hitting in the last two or three years,” he said. “I’m going for it, I’m more aggressive, and I have just a different approach to the semi-finals and finals of major events, especially when I’m playing two great champions, Rafa and Roger [Federer].

“In the last couple of years that wasn’t the case. I was always trying to wait for their mistakes and not really having the positive attitude, believing that I can win. So this has changed.”

For his part, Nadal said a poor serving day did not help his cause but he was delighted with the mental part of his game as he hit back in the third set. It was the best he has played in any of the finals against Djokovic and he said he was heartened by his effort.

“I go back home knowing that I am on the way,” he said. “Six straight loses, for sure that’s painful, but I’m going to work every day until that changes. It’s going to be tough to change the situation, but the goal is easy to see.”

McEnroe’s assessment that Djokovic is having the best year in the history of the sport is an interesting one, for the American compiled a stunning win-loss record of 82-3 in 1984. His loss in the final of the French Open to Ivan Lendl, having been two sets up, still hurts to this day but if Djokovic continues in the current vein, he could perhaps surpass his mark.

Had it not been for his defeat by Federer in the semi-finals at Roland Garros this year, we might even have been talking about him being the first man to complete the calendar grand slam since Rod Laver in 1969.

In an era of such physicality, winning all four in the same year has been beyond a host of great champions but does Djokovic think it’s achievable?

“I don’t want to say that’s not possible,” he said. “It’s possible, everything is possible. But still, it’s such a tough task to win all four grand slams in a year. How many players did it in all history?”

The answer to that is two: Don Budge in 1938 and Laver, twice, in 1962 and 1969. Could Djokovic be the third in 2012?

“If I make half what I’ve done this year next year I’ll be happy,” he said. “This sport is something that I love to do and it brings me joy every single time I step on the court and make a win. Nothing can replace that feeling.”