Djokovic beats Schwartzman in his ATP Finals opener

Djokovic's only loss in an opening match at this event came in his tournament debut in Shanghai in 2007.

"Back in 2007, [it] was my debut in Shanghai and I lost all three matches in the group... I think the format allows you really, even [if] you lose a match, to still have a chance to qualify for semifinals," Djokovic said after his match that lasted for one hour and 18 minutes.

"You have plenty of motivation in terms of points, in terms of financial incentive. Every match that you win, you get to win 200 points, which is almost as [much as] winning an ATP 250 event. There is plenty of motivation for Diego. I'm sure that he wants to try to play better than he did today," he added.

Djokovic won 65 per cent of his second-serve return points (13/20), showing great consistency. With his sixth win in as many ATP matches against Schwartzman, the 33-year-old equalled Andrey Rublev's Tour-leading total of 40 wins this season.

"The beginning of the match wasn't that great for me. He broke my serve in the third game and I managed to break [back]. It was a close encounter until I broke his serve at 4-3 and managed to close out the first set," said Djokovic.

"In the second set, I started swinging through the ball a little more [with] a bit less hesitation from both corners. I was very pleased with the way I played, especially in the second set," he added.

The ATP Finals brings together the best eight players of each year.