LONDON - World number two Novak Djokovic from Serbia vanquished Italian Matteo Berrettini 6-2, 6-1, winning the opening match at the ATP World Tour Finals here on Sunday.

Djokovic, 32, had never played against Berrettini before, who qualified for the season finale for the first time after reaching his career-high ranking of world number eight.

In the year-ending tournament, the five-time champion gave the debutant little chance on court, grabbing the victory after 64 minutes in the Group Bjorn Borg opener.

"I'm very pleased with the way I returned, knowing how good of a server he is and how strong and fast the serve is," said Djokovic. "I'm really happy with the way I was getting most of his serves back, especially from that moment on towards the end."

The 23-year-old Berrettini thought he played well on Sunday, but his rival was just much better.

"We were playing flat, fast, and he was moving better than me, was playing better than me. So it was tough to win the points," said Berrettini.

The other two players, Roger Federer and Dominic Thiem in the same group are going to lock horns later on Sunday and Djokovic is slated to meet Federer for the 49th time this week.

Djokovic didn't believe that the 5-set victory over Federer in this year's Wimbledon final could make any mental impact on the Swiss legend.

"Roger's experience and mental strength has been almost unprecedented. He's one of the greatest players ever to hold the racquet," said Djokovic. "His ability to recover after big losses and to cope with the pressure in tough moments on the court has been phenomenal over the years."

"When I play Roger, I know he's going to deliver his best tennis."