During Roger Federer’s hugely enjoyable defeat to Novak Djokovic in their opening World Tour Finals group match on Tuesday night, there was a moment when it became apparent that the Swiss master must go on playing until his legs beg him to stop.
A set and 2-1 down in the second stanza, Federer pulled out a marvellous hold to love, dispatched with the imperious arrogance that we saw so often in his pomp.
There were further moments of outstanding aesthetic and technical beauty, such as an impudent flicked return that caught Djokovic cold en route to a break of the Serb's serve, or the dominant tie-break that saw Federer level at one set apiece.
Whatever the detractors calling for his retirement may say, Federer is still the main attraction in men’s tennis. His popularity remains so much greater than that which accompanies Rafael Nadal (and that accompanied Pete Sampras) that you have to accept the sport of tennis is about much more than just the art of winning. Anyone present at the O2 or watching attentively at home would have noticed the bombastic roar that accompanied every flashing return, every crushing ace, every impudent flick of the backhand.
Federer's popularity is particularly notable when he plays indoors.
When the roof was called for in the second set of Federer’s 2012 Wimbledon final victory over Andy Murray, there was silent collective shrug among British tennis fans, probably including Murray himself.
A set to the good and apparently en route to a maiden Grand Slam title, the somewhat premature decision to draw Centre Court’s new roof – and spend the best part of 45 minutes allowing the court to acclimatise to the new conditions – played into Federer’s hands. For this was no longer a conventional grass-court final (grass being a surface that Murray has pretty much dominated in recent years), but an indoor title showdown. And Federer is arguably the greatest indoor player of all time.
Federer’s alarming 2013 slump is not entirely unexpected; the passing of time diminishes the physique and, while the Swiss was never overly reliant on strength or speed, the marginal decrease in his overall ability is inflated at the upper end of the rankings, in the latter stages of the five-setter.
But, as he showed in Bercy last week, Federer is still one of the sport’s prime indoor movers.
And again, even in defeat, in London Federer again proved he is a force to contend with under a roof.
Indoor tennis – particularly on the hard courts – is a technical leveller. The impact of the conditions is all-but eradicated, unless one has an aversion to the inevitable heat generated between a roof and four walls. You no longer have to hit through the wind or – in the case of the tactically unparalleled Murray – use the forces of nature to your shot-making and point-building advantage.
And technically Federer, still, is unrivalled. The delicate hands of Richard Gasquet and the searing winners of Stanislas Wawrinka come close, while the overall packages offered by Dokovic, Nadal and even Murray are of course now superior, but in terms of racquet manipulation and point anticipation Federer cannot be touched.
Realistically he will have to win most of his matches in two sets to have a chance of claiming a record seventh World Tour finals title; as soon as stamina and fitness enter the equation, the 32-year-old will struggle to cope with the power of Nadal, the flexibility of Djokovic (pictured at his bendy best below) and both men’s endless reserves of energy.
We saw that quite clearly tonight; Federer found the extra reserves needed to claw the second set back from Djokovic, but once it entered a third he faded badly. He simply cannot go the distance with the super-fit Serb – or Nadal, or Murray – at this stage of his career, certainly not enough regularity.
Of course Fed is unlikely to add another Grand Slam to his armoury; given the outstanding athleticism of the ‘big three’, he is unlikely to go the whole way in London (I would be delighted if he proves me wrong).
And of course the other big players are amazing to watch; in addition to his physical superiority and almost psychopathic mental strength, Djokovic also made some marvellous shots, such as the diving backhand across court that caught Federer cold during their second set tete-a-tete. Nole is clearly a vastly superior athlete and, as such, the better player.
But perhaps more than other sports, tennis is as much about entertainment as it is the pragmatism of victory. Gasquet, and fellow Frenchman Jo-Wilfried Tsonga, are equally unlikely to clinch an elusive Major, yet they remain immensely popular draws on the tour. Fabrice Santoro never broke into the top 10 but, a master of the trick-shot, he put bums on seats into his late thirties.
Should Federer wind down his career simply because he is no longer the best? Fans accustomed to his winning ways should remember that true support comes through thick and thin; even in the twilight of his career, Federer is still a joy to watch. Certainly more so than the drudgery of Nadal and David Ferrer's one-sided, baseline bar-fight earlier.
So just lower the expectation, sit back and prepare to be entertained, for aesthetically Federer remains the world’s number one.
Reda Maher – On Twitter @Reda_Eurosport