PARIS — Men's world No 1 Jannik Sinner revealed Wednesday he learned his trade alongside Roland Garros sensation Lois Boisson, after the 361st-ranked player extended her stunning run in Paris by reaching the semifinals on the women's side of the draw.

A video circulated on social media earlier in the day of the unlikely duo enjoying an early morning hitting session before playing their respective quarterfinal matches.

But Sinner told reporters after his straight-sets win over Alexander Bublik — where he booked his spot in the semifinal — that he and the French wildcard have known each other for years.

"We actually were in the same center for a little while back in the days," said the Italian top seed.

"And we practiced, you know, sometimes together even there. So I know her. It's now already a time ago."

Despite their hugely differing career paths since then, Sinner said he and Boisson had even had a catch-up shortly before the Dijon-native's ascent to stardom.

"I saw her before the tournament in the gym," he recounted. "We talked a little bit how things are, and she was very happy. Having a wildcard here, it's a special tournament for her, being French."

A relative unknown to the tennis world at large, Boisson has enjoyed a fairytale maiden Grand Slam appearance, ousting third seed Jessica Pegula and world No 6 Mirra Andreeva in successive matches to reach the last four in Paris.

In doing so, the 22-year-old became the lowest-ranked major semifinalist in the last 40 years, and also the new sporting icon of a nation.

"It's amazing, no?" said Sinner.

"I think that's exactly what France needs, you know, something very new, very special, great mentality.

"I think the level she produces is amazing, no? Very consistent. Very clay court style, you know, with the forehand, a lot of top spin."

Sinner got a close-up of that heavy top-spin style on Wednesday when knocking up with Boisson before the day's play.

And it was the three-time Grand Slam winner who did the asking.

"Today it was raining, so I called here, the desk, you know, if there was some free spot, because I don't want to risk to go on court without warming up," Sinner said.

"So we arrived here quite early. Yeah, she (Boisson) said straightaway yes, and we hit some balls."

Though they may be separated by 360 ranking spots, Sinner said he was impressed by Boisson's ball-striking ability.

"It was a very consistent warm-up for a different game style for a woman, because the ball is quite high and quite spinny," he said.

"Physically (she's) very strong. She deserves to be in the position where she is right now, and we wish her all the best for the future."

AFP