Novak Djokovic began his began his challenge for a hat-trick of ATP World Tour Finals triumphs in London with a 6-1 6-1 demolition of Croatia's Marin Cilic on Monday. The Serbian world number one produced a ruthless display against a ragged U.S. Open champion, opening his Group A account with a 56-minute masterclass. 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. Novak Djokovic raises his hands in victory after defeating Marin Cilic 6-1 6-1 at the ATP World Tour Finals
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Novak Djokovic defeated Marin Cilic 6-1 6-1 at ATP World Tour Finals
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World No 1 is favourite to win London O2 event and retain his ranking
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Stan Wawrinka earlier defeated Thomas Berdych by the same score
'Unfortunately, it was my worst match of the whole season, and I kept it for the start here in the @placeholder,' said Berdych.