In between there was the little sly dig where Djokovic told the world’s media that “Roger is moving maybe slower than he used to.”
You might almost say that Federer had a new nemesis to place alongside Rafael Nadal. Three years ago, his head-to-head record against Djokovic stood at 13-6 in his favour. After Tuesday night, he still leads the series, but only by a single match: 16-15.
And here is one potential downside to Federer’s resolute determination to keep pressing on with his playing career, perhaps until the Rio Olympics. Players he used to boss around are beginning to catch up with him. Some might even feel they have a score to settle, having been brushed aside by that magisterial forehand so many times in the past.
The fans, of course, just want Federer to keep playing until his racket arm drops off. They would rather see him win than lose, of course, and there was a sense on Tuesday of 15,000 people trying to blow his weaker shots up and over the net.
But they are happy just to see him at all, especially when he provides more than two hours of entertainment on the way to a 6-4, 6-7, 6-2 defeat.
In the case of some great champions — like Martina Navratilova — popular affection only develops once they start to show signs of mortality. Federer is different: he has been feted from his first grand slam to his last.
Last year, he had the greater share of crowd support against Andy Murray — then freshly returned from his breakthrough grand slam win in New York — when they met here at the O2. But all the support in the world could not help him against Djokovic, the man in black who was quite prepared to play the villain in this partisan arena.
After the match, Federer said he felt that neither man had played their best, because of the short turnaround between Paris and London and the difference in the speed of the two courts.
But there were still plenty of intricate rallies, and some winners that would grace any highlight reel. Federer’s inside-out forehand, the stroke that launched a score of trophies, was back on song.
So was Djokovic’s backhand pass, which tends to leave the net-rushing opponent looking as lost and helpless as though he had been stood up at a bar.
“I was actually feeling much better than I was in Paris overall physically,” said Federer. “But obviously it’s been a tough season overall. So I guess I’m just rattled at times, you know, with my level of play consistently.
“So I regret not having taken my chances better maybe, maybe played it a bit tougher, a little bit more solid overall. But there was some good tennis out there as well at times. There is something I can definitely take away from this match.”
Federer will probably need to defeat both his remaining opponents in the group, Juan Martín del Potro and Richard Gasquet, if he is to sneak into the semi-finals.
Meanwhile the battle to finish the year as No 1 rolls on, after Rafael Nadal beat David Ferrer in the first match on Tuesday.
Today’s action could be decisive, for if Nadal adds a second victory by beating Stan Wawrinka — again in the first match on court — he will move so far ahead that Djokovic could not possibly catch him until February, when he starts defending points again.
Even if he loses — and his record against Wawrinka stands at a spotless 11 wins from 11 attempts — he will have another chance against Tomas Berdych on Friday.
As a contest, Nadal’s match on Tuesday was the least gripping of the four singles encounters we have seen thus far. Ferrer only arrived in London on Sunday night, after falling just short of defending his Paris Masters title, and was visibly short of energy.
Still, this tournament needed a strong showing from Nadal to tee up the potential storylines for the coming weekend, and that is what it got. After a lacklustre week in Paris — by his own high standards — he has upped the ante here in London, as he chases the first World Tour Finals title of his extraordinary career.
Nadal said on Monday that he would prefer to see this tournament rotate around different venues, rather than always be played on an indoor hard court. Yet this is not to say that he dislikes the O2 Arena itself; only that the low bounce and slow speed of the playing surface can neutralise the threat of his famous forehand.
“Is one of the best stadiums that I ever played,” said Nadal. “For some reasons, you have places that the conditions are a little bit worse for you. But every time I am able to play in the World Tour Finals, it has been a special feeling for me.”
Perhaps the court is less hospitable to Nadal than it is to the three big threats lurking in the other half of the draw: Djokovic, Federer and Del Potro.
But then he has defied the odds many times already this season, in what Boris Becker has described as the greatest comeback year in tennis — and arguably in any sport. Who can be sure he will not do it again?