Andreeva, who was playing junior tennis just 18 months ago as a losing girls' finnalist at the Australian Open, showed no mercy to the ailing superstar who's won the senior title the last two years at Melbourne, the young Russian prevailing 6-7 (5-7) 6-4 6-4 in front of a stunned Court Philippe Chatrier crowd on Wednesday.
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.
Aryna Sabalenka needed pills to keep her going in her sensational Roland Garros loss. (AP PHOTO)
Either the 12th seed Paolini or unseeded youngster Andreeva, who's not yet won a senior title, will now battle for a wholly unexpected place in Saturday's Roland Garros final.
Nothing, though, could top the remarkable upset as 17-year-old French-based Andreeva 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 constant misery while the Belarusian, on an 11-match winning run at the slams after her Melbourne win, was clearly also suffering from some on-court ailment as she twice needed medication from a doctor, moved gingerly and constantly hunched over in some distress.
Andreeva, nerveless as she recovered from going a set down in a tight first-set breaker, then 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 admitted 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.
Jasmine Paolini also caused a big shock as she reached her first grand slam semi-final. (AP PHOTO)
The Belarusian hung on to take that set in a tight breaker, but soon looked in a world of discomfort, irritated after getting broken to go down 4-2 by hitting the ball away amid jeers and then getting a time violation too as she went down on her haunches, looking for a breather.
Sabalenka gambled on big hitting to get her out of trouble as moving around was obviously problematic, 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. Â
Earlier, in the same arena where compatriot Jannik Sinner had been crowned the men's new world No.1 less than 24 hours before, the diminutive 12th seeded Tuscan Paolini took full advantage of Rybakina's "not-the-greatest day at the office".
It's the first time an Italian man and woman have reached the semis in the same grand slam.
"It's an unbelievable feeling, it was a really tough match," beamed Paolini, who's just 1.63m tall but is big on spirit and talent.
The 2022 Wimbledon champion Rybakina coughed up a remarkable 48 unforced errors in a match that, at times, felt as if neither woman wanted to win, with 12 service breaks.
Ultimately, Paolini, a 28-year-old from Bagni di Lucca who accounted for Daria Saville in her first-round match, held her nerve far better in the denouement, as the Kazakh's game crumbled.
At 4-4 in the final set, Rybakina served up a terrible game, hitting first a simple backhand and then an equally straightforward forehand low into the net, before ballooning a forehand long to give Paolini the simplest key break.
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