ATP Finals 2018: Novak Djokovic taking nothing for granted vs Alexander Zverev

Novak Djokovic says his comfortable group stage victory over Alexander Zverev will count for nothing when the two meet again in the ATP Finals at London's O2 Arena this evening.

Zverev beat Roger Federer in straight sets on Saturday afternoon to book his place in the season-ending final, while world number one Djokovic will bid for his sixth win in the competition after dismantling Kevin Anderson 6-2, 6-2.

Djokovic beat Zverev 6-4, 6-1 in the round robin stage earlier in the week, but believes he will face a different challenge from the 21-year-old German tonight.

"I played very well in the group stage against [Zverev] but I don't think he was close to his best," Djokovic said.

"He had a great match against Roger [Federer] and he has been serving well, so it will be a similar approach as today [against Anderson], trying to get as many first serves back.

"It is the last match of the year for both of us so let the better player win."

Djokovic was in imperious form against Anderson, making light work of the South African's usually lethal serve, and agreed it was his most complete performance of the tournament so far.

"I think it was the best match I've played so far this week and it came at the right time," he said.