Stefanos Tsitsipas shocked six-time champion Roger Federer 6-3, 6-4 to reach the final of the ATP Finals in his tournament debut on Saturday. The Greek sixth seed, 17 years younger than his 38-year-old opponent, beat the Swiss at the Australian Open but had fallen to him twice since then.

Federer was unrecognisable from the player who dominated Novak Djokovic in his final round-robin match, struggling on serve and hitting a total of 26 unforced errors compared with just five against the Serbian.

But Tsitsipas belied his years with a performance full of confidence and grit, saving 11 out of 12 break points during the match. Coming into the match, the Greek 21-year-old led the tournament in service games won, with 35 out of 37.

Dominic Thiem defeated Alexander Zverev 7-5, 6-3 in the other semi-final and will now face Tsitsipas in the summit clash.

Twitter was mighty impressed by Tsitsipas’ performance on Saturday and marked him as a future Grand Slam winner.

Here are some reactions:

[With inputs from AFP]