Two months since being granted permanent residency, Kasatkina's hopes of becoming the first Australian woman to reach the quarter-finals since Ash Barty's triumphant year of 2019 finally unravelled 6-3 7-5 at the hands of her exceptional 18-year-old fellow Russian-born buddy.
The only other time the pair had played, in the final of last October's Ningbo Open in China, Andreeva had ended in tears and needed to be comforted by Kasatkina after blowing a 3-0 lead in the final set.
On Monday lunchtime, though, the French-based teen who's rocketed to No.6 in the world didn't let Kasatkina, 10 years her senior, off the hook on Court Suzanne Lenglen despite another nervy blip.
Kasatkina even earned a set point to level the match after rallying in gritty fashion but world No.6 Andreeva showed steely resolve to the win after a compelling 94-minute duel.
Defeat for Kasatkina meant the end of the green-and-gold singles challenge, but she could pride herself on having been the 'last Aussie standing' among the 16 starters in the draw.
"It was a hell of a match. I'm super happy I stayed calm in the second set when she raised her level. Honestly, I'm so happy I won. I hate playing against her, we practise a lot and even that is a torture," Andreeva said after the pals hugged at the net.
"My coach (Conchita Martinez) says you've got to practise with the people you don't like. That's why I practise with her because I hate her!" she added with a big smile.
A tactical affair between two mates with terrific all-court games - Andreeva comes over like a younger, more power-laden version of Kasatkina - broke out on Roland Garros's second biggest arena as the Aussie comfortably held her own at the start.
She even looked set to strike first in the seventh game, carving out two break points as Andreeva got a mite impatient.
But the youngster is as tough as she's gifted. She held serve then induced five errors from the Australian in the next game to annex the key break.
Under increasing pressure from the depth and accuracy of the teen's laser groundstrokes, Kasatkina scooped a backhand long to gift the first set in 40 minutes.
Her problems were immediately compounded when Andreeva pulled off a lovely move at the start of the second set, a neat drop shot followed by a lofted winning pass that sealed an immediate break.
Kasatkina had promised she was ready to "die on court" and she looked absolutely spent after prevailing in one remarkable 26-shot rally.
And that utter determination started to gnaw away at Andreeva as the Aussie reeled off four games in a row from 3-1 down to serve for the set.Â
But Andreeva immediately counter-attacked to break back, then battled to hold after Kasatkina earned a set point on the youngster's delivery at 5-4, only to be deprived by a powerful forehand.
Once back level, Andreeva began to dictate. One piece of amazing defensive retrieving also induced a dismal Kasatkina smash into the net, and enabled her to break to love.
She then sealed the deal on her second match point with Kasatkina hitting a forehand long.
Andreeva has now reached the quarters without dropping a set and she's the youngest to achieve back-to-back last-eight appearances since Martina Hingis 27 years ago.
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