Serbian World No.1 Novak Djokovic rolled over Japan's Kei Nishikori 6-1, 6-1 at the Barclays tennis World Tour Finals in London.
Djokovic began his title defence in fine form, dominating the No.8 and pushing his record for the season to 79 wins and 5 losses on Sunday, reports Efe.
A minute of silence was observed at the start of the match in memory of those killed in the terrorist attacks in Paris on Friday.
The 28-year-old Djokovic broke Nishikori early and took the first set in just 31 minutes.
Nishikori, who became the first Japanese man to play in the World Tour Finals last year, appeared unable to slow the world No.1 in the second set, which lasted just 34 minutes.
Djokovic, who won the year-end tournament in 2008, 2012, 2013 and 2014, has had one of the greatest years in tennis history, winning the Australian Open, Wimbledon and the US Open, as well as five World Tour Masters 1000 titles.
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The 10-time Grand Slam champion has failed to reach the final of only one tournament this season - an Australian Open tune-up event in January in Dubai, where he fell to big-serving Croatian Ivo Karlovic in the quarter-finals.
The World Tour Finals, which is being played at London's O2 Arena, is the biggest tournament on the men's tennis calendar after the four Grand Slams.