NOVAK DJOKOVIC remained on course to end the best season of his life with a fourth straight ATP World Tour Finals crown.

The world No.1 outclassed Rafael Nadal to win a surprisingly brief semi-final 6-3 6-3.

He did not face a single break point and will play either Roger Federer or Stan Wawrinka in the final on Sunday.

Djokovic said: "It was a great performance from the very beginning. I was trying to be aggressive and dictate the play, and I managed to pull out my best game when it was needed the most."

Djokovic and Nadal were meeting for a 46th time, with many of their previous encounters being gruelling epics full of brutal rallies, but here the Serb was just too good.

He is now level with Nadal at 23 wins apiece, the first time Nadal has not led a rivalry that dates back to the French Open in 2006.

Given Djokovic had won seven of their last eight matches and not dropped a set in three previous meetings with Nadal this year, it was perhaps unwise to expect anything less.

But, for once in a year where he has been utterly dominant, Djokovic wobbled a little in his final two group matches at the O2 Arena.

First he lost an indoor match for the first time in three years against Federer and was then below his best again in a tight win over Tomas Berdych.

Nadal, meanwhile, had rediscovered some form of old after a challenging year, winning all three of his group matches against Stan Wawrinka, Andy Murray and David Ferrer.

But from the moment Djokovic fired four clean winners to break to love in the second game of the match, the tone was set.

After three games Djokovic had blasted eight winners and made not a single unforced error.

David Beckham was among the capacity crowd, but the contest they would have wished for was not forthcoming as Djokovic comfortably held Nadal at arm's length.

The Spaniard had been aggressive in his play in the first three matches, finding depth and penetration with his groundstrokes, but they had little effect on Djokovic.

Nadal at least avoided being broken in the opening game of the second set but the pressure was relentless and it was no surprise when Djokovic moved ahead 3-2.

Serving to stay in the match Nadal could resist no longer and Djokovic clinched victory after an hour and 19 minutes, nailing a backhand winner down the line to bring up match point and then finding the opposite corner.

Remarkably, it was Djokovic's 30th win against top-10 opponents this year and put him through to a record 15th consecutive final.

Nadal said: "He was better than me and he deserved to do what he did during the whole season. He played just fantastic. When somebody's doing this, the only thing I can do is congratulate him and just wish him not the best of luck for the next year.

"Novak for the moment is almost unbeatable. But things are like this today. You never know what's going on in the future. I have been in very good situations a couple of times, then I get some injuries, things change. Not everything is that easy.

"What Novak is doing is just amazing. But it's not easy to stay at that high level for four years in a row or five years in a row."

Despite the loss, Nadal kept the positive attitude he has had all week and remains confident of a better season in 2016.

In 2011 and 2012 he lost seven straight matches to Djokovic, all in finals, but then turned the tables by winning six of the next seven.

He said: "I didn't have that kind of feeling, I was not that close against him yet. Against other rivals I was competing great, and that's it.

"As I said before the tournament, I was not able to think about Novak for the whole season. I have been playing in another league. It seems like the last month and a half, two months, I was in this top league.

"So my motivation and my goal is try to keep being in that top league, that is the top five, top four of the world."