PARIS, France - Unseeded Katerina Siniakova knocked out Maria Sakkari to claim a third round spot at the French Open, where World No.1 Naomi Osaka awaits.

The roller coaster encounter featured two tiebreaks and fourteen breaks of serve, with the Czech player emerging victorious to knock out the No.29 seed Sakkari, 7-6(5), 6-7(8), 6-3 in a three-hour and 14-minute epic.

Siniakova’s reward for reaching the French Open third round for the second year in a row? A showdown with top-ranked Osaka, who is going for her third consecutive Grand Slam title. Osaka triumphed 6-4, 6-0 in the pair’s only previous meeting last year in Dubai.

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Also in action on Thursday, Spanish qualifier Aliona Bolsova scored a big upset to knock out Sorana Cirstea in straight sets, 7-6(5), 7-6(3).

Bolsova, a Grand Slam debutante, spoke to after the victory, the biggest win of the 21-year-old Spaniard’s career.

“I could lose every single match this year after this and I think I would still be happy, because now I know that I can compete at this level and I can challenge people at the top of the sport, inside the Top 100,” Bolsova said. “This experience has given me so much confidence.”

She’ll take on Ekaterina Alexandrova in the next round, after the Russian player came back from a set down to oust former US Open champion Sam Stosur, 3-6, 6-1, 6-4.

Polish youngster Iga Swiatek is also through to the third round, scoring a dominant win over Wang Qiang, 6-3, 6-0.

“I don't have any [expectations], and that's kind of cool because I'm not stressed or anything,” Swiatek told press afterward. “I don't expect to win because I'm, like, new here. So I don't even know who I'm playing next. I'm not prepared. So we'll just see.

“And I hope I'll play my best tennis. Even if I lose, I just want to feel good on court and show my best.”

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Swiateki’s third round opponent will be Olympic gold medalist Monica Puig, who scored a 6-3 6-1 victory over Daria Kasatkina earlier in the day.

Joining them in the third round are Andrea Petkovic, who defeated Hsieh Su-wei 4-6, 6-3, 8-6, and Irina-Camelia Begu, who knocked out Karolina Muchova 1-6, 6-3, 6-4.