Mensik and Fonseca, aged 20 and 19 respectively, are tipped to be among the players who could challenge Jannik Sinner and Carlos Alcaraz at the very top of men’s tennis over the next few years – and their last-eight tie demonstrated why.

Both men were playing in their first major quarter-final and while Mensik confessed to feeling some early nerves in his post-match interview, his dominant serve proved critical as he moved into a two-set lead without facing a break point.

Fonseca had twice come back from two sets down to win matches at this year’s French Open, most notably in the third round against 24-time Grand Slam champion Novak Djokovic.

There were flashes of brilliance from the Brazilian throughout, but another mammoth comeback proved beyond him on this occasion under the roof on Court Philippe Chatrier.

The third set went on for close to 80 minutes, with Fonseca twice moving a break of serve ahead before being dragged back to parity by Mensik.

Serving at 6-5 down, Fonseca saved six match points in a marathon 12th game of the set before forcing a tie-break – which Mensik controlled to complete a 6-4 6-3 7-6 (7-3) victory.

“At the end of the match, there were some incredible shots,” said Mensik, a former Masters 1000 champion in Miami.

“I’m super happy that I’m the one that came back. I was a break down a couple of times but I managed to stay focused, stay in the match and keep fighting until the end.”

Mensik is the first Czech player to reach a Grand Slam men’s singles semi-final since Tomas Berdych at Wimbledon in 2017 and he is projected to move back into the world’s top 20.