Roger Federer beaten by Alexander Zverev at the semis of the Nitto ATP Finals

Six-time champion Roger Federer was making his 15th semi-final appearance at the Nitto ATP Finals in what was his 16th entry to the tournament. A 5-7, 6-7 (5-7) loss to Next Gen superstar 21-year old German Alexander Zverev means that Federer will have to wait till the start of 2019 to reach a historic century of ATP title wins.

Zverev was booed after the completion of the match as he had stopped a point in the tie-break when a ballboy dropped a ball. Zverev had his Naomi Osaka moment as he apologized to the crowd and to Federer in his post-match interview. "I apologised to Roger at the net already, he said it is okay and it is in the rules," the world number five said. This is well and truly the biggest win of 'Sascha' Zverev's blossoming tennis career.

With 3 ATP Masters 1000 titles already in his trophy cabinet, Zverev will look to add the biggest one yet of his career when he takes on either Novak Djokovic or Kevin Anderson in the Finals.

There was very little to separate the perennial fan favourite and the blonde-haired youngster for the first half hour or so. Both players resolutely held on to their service games before Zverev broke Federer's serve in the 12th game to take the first set 7-5.

It was Federer who grabbed the first break of the second set to take a 2-1 lead. Zverev answered back with a break of his own silencing the boisterous Federer fans. Both players managed to hold on their serves after that and the set went to a tiebreak. Both players got off to a good start holding their service points. An uncharacteristic volley by Federer into the net which should have been a routine put away earned Zverev the crucial mini-break. That was all that separated the two men as Zverev closed out the match.

The match ended on a rather unpleasant note, though, when one of the ball kids dropped a ball during a rally during the breaker. Zverev legitimately stopped play but the Federer fans who were clearly the majority in the crowd were unhappy that the point was replayed.

Zverev is the youngest player to make the Nitto ATP Finals since Juan Martin Del Potro in 2009.