Novak Djokovic hopes to punish Kei Nishikori for New York nightmare

 Novak Djokovic has warned Kei Nishikori there will be no repeat of his shock US Open loss to the Japanese star when they meet in the ATP Tour Finals on Saturday.

London: Novak Djokovic has warned Kei Nishikori there will be no repeat of his shock US Open loss to the Japanese star when they meet in the ATP Tour Finals on Saturday.

Djokovic booked a semi-final showdown with Nishikori after finishing top of Group A thanks to a 6-2, 6-2 rout of Tomas Berdych at London`s O2 Arena on Friday.

The victory also guaranteed the Serb would finish top of the year-end world rankings for the third time in four years.

But Djokovic didn`t plan to celebrate that impressive accomplishment for too long before he focused on the tough challenge posed by Nishikori.

The Japanese player, making his Tour Finals debut, has enjoyed a breakthrough year featuring a four-set win over Djokovic in the US Open semi-finals in September.

That loss was one of the few low moments for Djokovic in another tremendous year.

But Djokovic has been unstoppable at the Tour Finals for the last three years, winning 13 successive matches and stretching his unbeaten run at indoor events to 30 matches.

He believes that fine form and his extra experience under the O2 dome will help avenge the loss in New York.

"It`s obvious that he`s experiencing the best season of his life. He`s top five in the world. He`s playing some great tennis," Djokovic said.

"He`s one of the quickest players around. Deservedly he`s in the semi-finals on his debut.

"But, again, the conditions indoors and outdoors, where I lost to him in US Open, are quite different.

"I`m feeling pretty confident playing now. So it`s going to be good, high-class tennis."

It has been a landmark year on and off the court for Djokovic, who won a second Wimbledon title only a few days before marrying his long-time partner Jelena.

The couple celebrated the birth of their first child, Stefan, three weeks ago.

And he can cap a season to remember by becoming the first man since Ivan Lendl in the 1980s to win the Tour Finals three years in a row.

"It`s a great deal of happiness knowing what I`ve been through the entire season in order to get to where I am and finish the year as number one," Djokovic said.

"I know how difficult it is. It`s why I`m proud of this achievement.

"Being number one of the world is the pinnacle of the sport. Winning grand slams also is something that allows you to write the history of this sport.

"It`s difficult to say what is more important. But both these goals are always my goals at the beginning of the season. So I`m glad I managed to achieve both."

His joy at finishing on top of the rankings was a stark contrast to the gloom that pervaded the Djokovic camp after he lost a Grand Slam final for the fifth time in six attempts against Nadal at the French Open in June.

The Serb bounced back a month later when he enjoyed an epic five-set win over Roger Federer in the Wimbledon final and he insists there are no regrets about his slips in Paris and New York.

"I think I had a great season and great year overall for my private life and professional as well. Considering all the things that have happened and circumstances, I thought I have done very well," he said.

"A few matches here and there I wish I could have played better. Maybe the Roland Garros final or US Open semis. But I don`t want to go back and regret something that has already happened."