Bianca Andreescu became the highest women's seed to fall at the French Open so far as she lost a three-hour marathon match against Tamara Zidansek in the first round on Monday.
The former U.S. Open champion, seeded sixth, went down 6-7(1) 7-6(2) 9-7 to the Slovenian.
Canadian Andreescu, 20, served for the match at 5-4 in the deciding set but Zidansek broke back before missing a match point of her own in a gripping finale.
Andreescu found herself in trouble again serving at 7-8 and this time was unable to dig her way out of trouble with world number 85 Zidansek winning in three hours and 20 minutes.
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While on paper it was a shock, Andreescu was playing at only her third Tour-level claycourt tournament and her lack of experience on the surface ultimately proved decisive.
The women's draw lost another big name when former French Open semi-finalist Kiki Bertens fell at the first hurdle, losing 6-1 3-6 6-4 to another Slovenian Polona Hercog.
Marketa Vondrousova, the 2019 runner-up who is seeded 20th this year, managed to avoid an early exit, battling back from a set down to beat Kaia Kanepi 4-6 6-3 6-0.