Debutant Stefanos Tsitsipas caused a major shock by ending Roger Federer’s chances of landing a record-extending seventh ATP Finals to reach Sunday’s showpiece.

The Swiss master, who was aiming to reach Sunday’s showpiece of the ATP Finals for an 11th time and first since 2015, was bettered by the young pupil from Greece as Tsitsipas landed a breathtaking 6-3 6-4 victory to make it through to the final.

Tsitsipas will now face Austrian Dominic Thiem, who defeated defending champion Alexander Zverev in the second semi-final.

The Greek had already beaten Federer at the Australian Open earlier this year The Greek had already beaten Federer at the Australian Open earlier this year The Greek had already beaten Federer at the Australian Open earlier this year

A year after winning the Next Gen ATP Finals in Milan, Tsitsipas is aiming to follow Zverev as the second successive 21-year-old champion and the 6ft 4in Greek made the perfect start by winning four of the opening five games as the pair went toe-to-toe.

Crowd favourite Federer, who recorded his first win in four years over arch-nemesis Novak Djokovic to reach the last four, failed to take advantage of three break points in the seventh game – six in total – with those opportunities proving costly in the end as Tsitsipas eventually won a marathon 15-minute ninth game with his seventh set point.

Federer struggled to cope with the power of Tsitsipas from the back of the court Federer struggled to cope with the power of Tsitsipas from the back of the court Federer struggled to cope with the power of Tsitsipas from the back of the court

Tsitsipas, playing his 96th match of 2019, was put through his paces in a three-set loss to world No 1 Rafael Nadal on Friday, but he was revelling in the atmosphere of 17,500 spectators as he took advantage of a plethora of unforced errors from the Swiss to break to love in the third game of the second set.

Federer had maintained his proud record of having never failed to reach the semi-finals here at London’s O2, but he appeared to be down and out until he finally made a breakthrough with a 10th break point of the match to restore parity at 2-2 as his legion of fans chanted his name in unison.

The Swiss legend [right] failed to master the pupil in a major upset The Swiss legend [right] failed to master the pupil in a major upset The Swiss legend [right] failed to master the pupil in a major upset

It was, however, to be short-lived as Tsitsipas edged ahead in the very next game and that proved to be the pivotal moment in the match as he extinguished any hopes Federer had of making a comeback.