Elina Svitolina saved three match points to eliminate last year's runner-up Jasmine Paolini and book her place in the quarter-finals at the French Open on Sunday.
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The 30-year-old 13th seed roared back to upset the world No 4 4-6, 7-6 (8/6), 6-1 in their last-eight tie.
"I still cannot believe that this match finished my way," said Svitolina.
"It was a really difficult match today, Jasmine was playing really well. It was really tough for me but I'm very happy I was able to stay composed and fight until the very last point."
Svitolina will next face either triple-defending champion Iga Swiatek or former Wimbledon winner Elena Rybakina for a spot in the semi-finals.
The Ukrainian has never progressed further than the last eight in Roland Garros, falling at that stage four times since her Paris debut 12 years ago.
Paolini, who prepared for her tilt at the Coupe Suzanne Lenglen by winning the Italian Open earlier in May, has now fallen to Svitolina in both Grand Slams so far this year.
In the third round of the Australian Open, the Italian world No 4 won the opening set before Svitolina staged a comeback and won the third set to love.
On Court Philippe Chatrier, Svitolina forced a decider by outlasting her opponent in a topsy-turvy tie-break after Paolini passed up three match points in the second set, including one in the breaker.
"It was extremely tough but I'm very pleased I was able to win that second set," said Svitolina, adding her future in the tournament had hung on just two or three points in the set which lasted over an hour.
Svitolina then built on that momentum by racing into a 4-0 lead in the third set, before serving out the win at the first time of asking after nearly two-and-a-half hours of battle.