Roger Federer will have to wait until the 2019 season for a chance to reach 100 career titles after his semi-final defeat by Alexander Zverev at the ATP Finals.

Zverev, 21, tipped by many as a future Grand Slam champion, triumphed 7-5 7-6 (7-5) over the 37-year old at London’s O2 Arena.

Zverev faced boos at the end of the match after he had – legitimately – stopped a point in the tie-break when a ballboy dropped a ball.

In scenes comparable with Naomi Osaka’s victory speech at the US Open when her win was overshadowed by Serena Williams’ outbursts, Zverev was left apologising to both the crowd and Federer after one of the biggest wins in his career.

“I apologised to Roger at the net already, he said it is OK and it is in the rules,” the world number five said.

“I’m sorry this happened. I didn’t mean to upset anybody.”

The German Wunderkid will face Novak Djokovic or Kevin Anderson, who play later on Saturday.