Five-time champion Novak Djokovic began his attempt to equal Roger Federer's record number of ATP Finals triumphs on Monday with a straight-sets 7-6 (7-4), 6-2 win over Casper Ruud. 

After his match, Djokovic was presented with the trophy for finishing the year ranked No. 1, a feat he accomplished for a record seventh time – breaking a tie with childhood idol Pete Sampras. 

Djokovic attracted wild applause from the Turin crowd when he insisted on speaking in Italian for his on-court interview. 

"It's one of the most difficult things to do in our sport, to finish No. 1 at the end of the year, you have to play really well, consistently and with a lot of success throughout the year on every surface. I'm very proud," the 34-year-old Serb said. 

He added that he did not have a number in mind for how many more years he wants to play. 

"I don't want to impose a limit to myself at all, because I still enjoy playing tennis, and I really enjoy competition and playing at the highest level," the 20-time Grand Slam champion said. "Being No. 1 in the world, there is no reason for me yet to think about leaving tennis. I really am in a good place at the moment." 

Djokovic took a two-month break after losing to Daniil Medvedev in the U.S. Open final in September, which ended his pursuit of a calendar-year Grand Slam, but he returned this month to win the Paris Masters and has now won six straight matches. 

In the other group match at ATP Finals on Monday, Andrey Rublev topped 2018 champion Stefanos Tsitsipas 6-4, 6-4. 

Daniil Medvedev and Alexander Zverev won their group singles on Sunday. 

(With input from AFP, AP)