Novak Djokovic produced a masterclass on Saturday to crush Kevin Anderson and set up a title decider at the ATP Finals against Alexander Zverev, who ousted Roger Federer after a bizarre incident involving a ball boy.

World No. 1 Djokovic comfortably saw off the fourth seed 6-2, 6-2 never looking remotely troubled as he targets a record-equalling sixth end-of-season title at London's O2 Arena. "I'm very pleased I'm able to play at a high level consistently week after week for the last six months," said Djokovic.