Djokovic back in the groove

Novak Djokovic started his bid for a third successive ATP Tour Finals title with a sublime 6-1, 6-1 victory over Marin Cilic at London's O2 Arena on Monday.

Djokovic took just 57 minutes to thrash US Open champion Cilic as the world number one extended his winning run at indoor events to 28 matches, a streak that includes 11 consecutive victories at the Tour Finals.

The Serb, who has already triumphed in London at Wimbledon earlier this year, is bidding to become the first man to win the Tour Finals three times in a row since Ivan Lendl from 1985 to 1987 and he looks in the mood to do just that on the evidence of his latest masterclass.

"It's been a great, great match. I haven't played here for 12 months, it's great to be back. It was a great performance," Djokovic said.

"Marin as a US Open winner has a lot of confidence, but I managed to neutralise his serve and get a lot of ball back in play and that was part of the tactic."

Djokovic arrived in London in buoyant mood after celebrating the birth of his first child, a boy named Stefan, by winning the Paris Masters without dropping a set earlier this month.

He has the additional motivation of knowing if he wins all three of his group matches he will be guaranteed to hold off Roger Federer in the race to finish the year on top of the world rankings.

The 27-year-old, looking to become only the fifth player to win the Tour Finals four or more times, had won all 10 of his previous meetings with Cilic, including a five-set victory in this year's Wimbledon quarterfinals, and once again the Croatian had no way of stopping his rival.

Cilic, making his Tour Finals debut after winning his maiden Grand Slam crown at the US Open, is capable of using his height advantage to overpower opponents with his booming serves.

But in Djokovic he faced one of the greatest returners of all time and the Serb wasted little time neutralising Cilic's biggest weapon as he broke serve in the third game.

On the few occasions Cilic managed to get into a prolonged rally, the champion's flawless groundstrokes invariably overwhelmed the Croat and he was broken again in the fifth game as Djokovic took the first set with ease.

Djokovic's remarkable ability to chase down lost causes was driving his opponent to distraction and the Serb broke in the second game of the second set thanks to another tremendous piece of defensive play.

Earlier on Monday, Switzerland's Stan Wawrinka opened his Group A campaign in scintillating style with a 6-1, 6-1 demolition of Tomas Berdych.