As the children were bidding adieu to the arena after the US Open final, a reporter in the press centre remarked on the enduring strength of tennis’s elder statesman. “No one is unbeatable,” he remarked, “which is the beauty of tennis.”

At the time, no one could be sure if the comment referred to the US Open trophy that Djokovic had just won. But afterwards, Djokovic picked up the phone and called up the journalist himself, and confirmed that what he had been thinking had been true. The only thing that kept tennis’s biggest star from winning a tennis match for 24 grand slams was the unyielding will of his opponent.

So, if Djokovic was, and is, unbeatable, what happens next? The match against Federer in the Australian Open final will be the 31-year-old’s 10th final at a grand slam.

After losing so many of them, Djokovic might appear to be a beaten man. But he’s not.

Young gun

Novak Djokovic is now back on top after almost 18 months away from the courts. Photo: Fred Duran/Getty Images

Djokovic was seriously injured and out of the game for the best part of 18 months. But when he was sidelined he did what most of us would do – he went on holiday.

The world number one told the BBC that he spent a long period on a yacht, focusing on his fitness, new tennis skills and what he dubbed “life lessons.”

“I did a lot of swimming, because that’s always been a big part of my life,” Djokovic said. “I did a lot of yoga, which had been something I was doing in the past on my holiday.”

Being back on top after all those months off is not a surprise. The Serbian has, after all, won 13 major titles – third only to Nadal and Federer – and made history along the way. He is an apt blend of athleticism and power, and at 26 he has more than enough experience to have honed all of his tennis skills and, arguably, should be ahead of many of his peers in their peak years.

Remain supreme

The US Open is Djokovic’s eighth victory over Federer in 11 major finals. Photo: Tom Jenkins/Getty Images

After his latest victory in New York, Djokovic conceded that he hadn’t expected to come out on top in his own epic showdown with Federer. But he also insisted that he believed he could come out on top against any opponent, as long as he remained supreme.

Federer will certainly be trying to prove his own resilience this week at the ATP World Tour Finals in London, where Djokovic, with his long history of winning Masters 1000 titles, is on top of the order of merit and is the clear favourite to lift the trophy. He is also the clear favourite to win both the singles and doubles at the ATP World Tour Finals.

That seems unlikely, however, according to some. Roger Federer will find some demons within himself at the ATP World Tour Finals this week. Photo: Damien Meyer/AFP/Getty Images

“He could beat anyone at the moment,” said Filippo Iacopelli, who has observed Djokovic at close quarters since the mid-1990s.

“Everything he touches turns to gold, but again I wouldn’t be surprised if he loses.”

Time and again, Djokovic has proved his superior skill and stamina. With his great physical prowess and towering serve, he is less a tennis player than a blacksmith with a wooden club and a metal wheel.

It is unfair, however, to write him off as any one match, or one tournament, too far. Djokovic and Federer have pushed each other to the limit for decades, and will continue to do so on and off the court.