World number one Novak Djokovic took a big step towards the semi-finals at the ATP Finals with a clinical victory over Alexander Zverev.
After a very physical and close first set, the Serb ran away with the second to win 6-4 6-1.
Djokovic, chasing a first ATP Finals title since 2015, will reach the last four if John Isner beats Marin Cilic later on Wednesday.
“I don’t think it was breathtaking tennis but a win is a win,” he said.
“I played well mid-way through the second set and started to swing through the ball.
“I had not served that well but he made a lot of unforced errors which helped me to win.”
Indeed, it was a double-fault from Zverev that handed Djokovic the first set and a total of 33 unforced errors that contributed to the 21-year-old’s downfall.
Djokovic plays Cilic in his final round-robin match on Friday, while Zverev takes on Isner.