London: Roger Federer produced another masterly display to beat Japan’s Kei Nishikori 6-3, 6-2 and move a step closer to the semi-finals at the ATP World Tour Finals on Tuesday.

Novak Djokovic, meanwhile, began his challenge for a hat-trick of Finals triumphs with a 6-1, 6-1 demolition of Croatia's Marin Cilic on Monday.

The 27-year-old has now won 28 consecutive matches indoors dating back to 2012 and should he win his remaining two group matches against Stanislas Wawrinka and Tomas Berdych he will be guaranteed to end the year on top of the rankings.

Although this year’s tournament is still to witness a three-set match, the entertainment served up by world No. 2 Federer and Asian trailblazer Nishikori kept the capacity O2 crowd enthralled for one hour and nine minutes.

Federer clearly enjoyed it too. “I was expecting a very difficult match,” the 17-time Grand Slam champion said on court, to cheers from a vocal Swiss contingent complete with cowbells.

The 33-year-old Federer, who can still knock Djokovic off the top of the rankings before the end of the year, fought off two break points in the third game, one with an ace, and broke himself a game later with a flowing forehand pass.

That was enough for the Swiss maestro to secure the opener and the quality of his play pressured Nishikori into several errors on the backhand side at the same stage of the second set as he forged further into the distance.

There were flashes of inspiration by Nishikori, a graceful top-spin lob here, a sweetly-struck backhand pass there, but he lacked the authority he showed in convincingly beating home favourite Murray on Sunday.

Federer, who began his record 13th appearance at the ATP Tour Finals by subduing Raonic in straight sets, has only once failed to survive the group stage and looks poised to take centre stage again at the weekend.

Cilic, on the other hand, won the opening five points of the match but his debut at the ATP’s prestige event quickly turned sour as Djokovic turned up the heat with a clinical display.