Teenager Mirra Andreeva delivered one of the great French Open upsets overnight, sending the poorly world No.2 Aryna Sabalenka crashing out in the quarterfinals at Roland Garros.

Andreeva, who was playing junior tennis just 18 months ago as a losing girls' finalist at the Australian Open, showed no mercy to the ailing superstar — winner of the main title the last two years at Melbourne Park.

The young Russian prevailed 6-7 (5-7), 6-4, 6-4 in front of a stunned Court Philippe Chatrier crowd on Thursday morning (AEST), before Australia's Alex de Minaur took to the court in his loss to Alexander Zverev.

It was the second major surprise of the day after the Italian success story at Roland Garros continued with Jasmine Paolini reaching her first ever grand slam semi by shocking a curiously out-of-sorts Elena Rybakina 6-2, 4-6, 6-4.

The 12th seed Paolini and unseeded youngster Andreeva, who's not yet won a senior title, will now battle for a wholly unexpected place in the Roland Garros final.

France-based Andreeva, 17, became the youngest grand slam semi-finalist since a 16-year-old Martina Hingis at the US Open in 1997.

She made Sabalenka's life a misery, while the Belarusian was clearly also suffering from an ailment as she twice needed medication from a doctor, moved gingerly and constantly hunched over.

Andreeva, nerveless as she recovered from going a set down in a tight first-set breaker, never got off Sabalenka's case — reducing the most powerful hitter in the women's game to a defensive shadow.

"Me and my coach (former Wimbledon champ Conchita Martinez) had a plan today, but again I didn't remember anything," the teenager said on court, to much laughter.

"I just try to play as I feel and that's it."

That free spirit was enough to keep a sub-par Sabalenka under constant pressure, after Andreeva had scented weakness in the opening set when the double Australian Open champ called the trainer.

The Belarusian hung on to take that set, but soon looked in a world of discomfort.

Irritated after getting broken to go down 4-2 she hit the ball away amid jeers and then got a time violation as she went down on her haunches, looking for a breather.

Sabalenka gambled on big hitting to get her out of trouble, but Andreeva kept her on the move in the final set.

With Sabalenka serving to stay in the match, Andreeva crushed a terrific backhand winner to earn a second match point, and then clinched victory with a delightful backhand lob after just under two-and-a-half hours.

Earlier, in the same arena where compatriot Jannik Sinner had been crowned the men's new world No.1 less than 24 hours earlier, the diminutive Paolini took full advantage of Rybakina's "not the greatest day at the office".