Stefanos Tsitsipas set his sights on grand slam success after his stunning “rollercoaster” victory over Dominic Thiem at the ATP Finals.

The 21-year-old from Athens came of age at London’s O2 Arena, becoming became the youngest winner of the prestigious season-ending tournament since Lleyton Hewitt in 2001, and the youngest debutant to lift the trophy since John McEnroe back in 1978.

Just a year after winning the NextGen Finals, for players of 21 and under, Tsitsipas mixed it with the very best on the bank of the Thames and came out on top.

Congratulated by his country’s prime minister Kyriakos Mitsotakis after his semi-final win over Roger Federer, Tsitsipas went on to write his name in Greek sporting history with a 6-7 (6) 6-2 7-6 (4) victory.

It was only the third time in 16 years that the final did not feature at least one of the ‘big three’, Rafael Nadal, Novak Djokovic or Federer, and further evidence surely that the long-awaited power shift in men’s tennis is finally on the way.

At 26 Thiem is just about part of that youthful scene as well, and his notable wins over Federer and Djokovic this week helped him climb to fourth in the world.

But the final belonged to Tsitsipas and the legions of Greek fans who made the 02 feel like a home from home for the new champion.

Stefanos Tsitsipas described his win as a rollercoaster
Stefanos Tsitsipas described his win as a rollercoaster (John Walton/PA)

He said: “It’s been a rollercoaster. It’s a dream come true and the best way to end this match.

“My fighting spirit and me constantly trying to push myself to do better got me there in the end.

“Things were great this year and I beat some top-ranked players which gave me confidence, and I’ve won matches in grand slams and Masters 1000s. I think I can do well in the slams.

“I feel like my game is getting better over time, and I believe I’m really close on being crowned a grand slam champion. I know these are strong words that I say, but I do feel like I belong there.”

The two players are close friends on the Tour –  Tsitsipas even acted as Thiem’s hitting partner at the tournament in 2016 – and they embraced at end of a gruelling encounter.

A nip-and-tuck first set went to a tie-break, and when the score reached 7-6 each player had won 44 points. But crucially, Thiem had the ball in his hand and an unreturnable first serve clinched the opening set.

Yet if that was tight, the second was a walkover as Tsitsipas broke twice, raced into a 4-0 lead and confidently served it out.

The first set had taken over an hour, the second lasted 26 minutes in a blur of shaggy hair and flamboyant shot-making, and all Thiem’s good work had unravelled.

Dominic Thiem looked back on some amazing wins despite losing the final
Dominic Thiem looked back on some amazing wins despite losing the final (John Walton/PA)

When Thiem netted a backhand Tsitsipas had an early break in the decider, but the Greek began bearing gifts and three wayward backhands allowed Thiem to draw level.

But it was a horrible, wafted forehand from Thiem which handed Tsitsipas the initiative in the deciding tie-break, and a memorable victory was wrapped up in two hours and 34 minutes.

Thiem said: “It’s always going to be like that in tennis. That’s why it’s probably mentally the most brutal sport existing because you can play such a great match and end up losing in the championship match.

“From that point of view, it’s a very disappointing loss, very hard to digest. But I had some amazing wins also, even this week, that got me in this situation even to play at the Finals. So it’s fine.”