Jannik Sinner’s First Sport Was Skiing. It’s Helped Him Play Fearlessly in Tennis.

“Not the easiest thing, for sure,” Sinner said of that challenge.

Sinner’s biggest career achievement before the French Open came last year, when he won the ATP Next Gen event for players 21 and younger. At only 18, he blitzed the field while playing in a quicker format.

This French Open quarterfinal against Nadal will be Sinner’s first match facing any of players who make up the Big Three of men’s tennis, including Novak Djokovic and Roger Federer. Still, in the lead-up to the French Open, Sinner practiced on consecutive days with No. 3 Dominic Thiem, the No. 1 Djokovic, and No. 2 Nadal.

Nadal said that he has seen Sinner “improving every single week” of the tour.

“He has an amazing potential,” Nadal said. “He moves the hand very quick and he’s able to produce amazing shots.”

The speed of Sinner’s improvement was also noticed by the sixth-ranked Stefanos Tsitsipas, who beat Sinner in straight sets at the Italian Open last year, then lost to him 16 months later at the same event.

“For sure, we can see a great future, see him do good things on the circuit,” Tsitsipas said. “I would not be surprised, yeah, if he has good wins against the top five and the top three. Why not? He has a very big game, a very talented player. I think he is a hard-hitter as well, which makes it difficult.”

When Sinner got the best win of his career on Sunday at Roland Garros, beating the recent United States Open finalist Alexander Zverev, 6-3, 6-3, 4-6, 6-3, in the fourth round, his celebration was muted, simply holding up his right fist as he walked up to the net.

“Still a lot of work to do,” Sinner said after the match. “Physically, technically, everything. It’s, yeah, a long way.”