Fair enough, too. The next two players to try will be Roger Federer, on Tuesday, and then Tomas Berdych, world No.8 Kei Nishikori having been blitzed 6-1, 6-1 in the opening Group Stan Smith round-robin match of the ATP World Tour Finals. Djokovic's 23rd consecutive win was punishing, immaculate, complete.

"I think I was at my best," the 28-year-old declared, rather ominously for those who would seek to deny him a record fourth consecutive title at the season finale to ink the exclamation mark on an outrageously good year.

"Undoubtedly it's been an incredible performance that I was hoping I can have coming into the match, coming into this tournament where I've had a great record in last couple of years. Reflecting back on those memories of course gives me more confidence, more comfort coming into every single match."

More confidence? It scarcely seems possible. Yet for all that Djokovic has achieved in 2015, including three of the four majors among 10 titles before Sunday night's presentation of his fourth year-end No.1 trophy since 2011, the clear message is that while there is still a finish line to be reached, so there will be a lunge. Berdych said on Friday that the Serb would not lose unless his level drops, and there was no sign of that against Nishikori. Quite the opposite.

The Japanese world No.8 gave some insight into the difficulty opponents face when he said that, yes, he had served poorly, but no, he had not played  badly. "Today [I] couldn't do anything," said the 2014 US Open finalist, whose lowly first-serve percentage left him scrambling to play defence against the master of it. Which was never going to end well.

Not that it was always like this, and there are many factors, Djokovic said, why it now is. "I've had that great joy to win a first grand slam (the 2008) Australian Open when I was 21 years old," he said. "Ever since then to this point, it's been seven years of a long process of learning, ups and downs, doubts, self-belief, some tough moments where I even considered of not playing tennis back in 2010."

This week, Federer is his main group rival, the Swiss having the unique distinction of beating Djokovic twice in 2015 - on Dubai and Cincinnati hardcourts. Stan Wawrinka (French Open), Ivo Karlovic (Doha) and Andy Murray (Montreal) are the other players responsible for any minor imperfections on an outstanding record that now stands at 79-5.

Yet Federer's (60-10) is also very tidy by most standards, and after a tardy start against Berdych, the Swiss third seed prevailed 6-4, 6-2 with the aid of 20 aces to proceed to a 43rd career meeting with Djokovic. Overall: 21-21. This year: 4-2 to Djokovic, including both grand slam finals, at Wimbledon and the US Open.

Asked whether the gap was as big as it appears, six-time champion and 17-major winner Federer said that depends on who was looking. "I don't think I'm that far off. Then again, let's speak in two days. Two days is not the match that I care the most about, to be quite honest. It's an important match, very important. But it's not the match. It's going to be interesting to see how I play that one. I'm curious to find out myself."

A minute's silence to honour the victims of the Paris terrorist attacks was observed before the first singles match, but it continues to be Djokovic making all the loudest on-court noise. "Undoubtedly it has been the best season, the best year, of my life," he said during the trophy presentation. "I have been experiencing the most of my abilities in my tennis game. Everything has come together over the years and I've been very consistent with my results... This is the crown for all the achievements in the season."