Doubles specialist Kateřina Siniaková of the Czech Republic put Osaka under pressure from the off and needed just 77 minutes to oust the Japanese world number one.

It was a case of what might have been for Osaka, who failed to convert seven break points against her rival.

Instead, she was broken three times and amassed 38 unforced errors.

Siniaková, world-ranked 42, will face 14th seed Madison Keys in round four after the American defeated Anna Blinkova 6-3, 6-7, 6-4.

Tenth seed Serena Williams was another big casualty as the women's draw was thrown wide open.

American compatriot Sofia Kenin blew away Williams in the first set with 83 per cent of first serve points won.

She backed it up with two breaks of serve to clinch a 6-2 lead.

Williams raised her game and it seemed normal service had resumed when she broke back at 3-3 in set two, but Kenin earned the crucial break at 6-5 and served the match out 6-2, 7-5.

The win was the biggest of Kenin's senior career, her previous best being two third-round appearances at the US Open.

She will meet eighth seed Ashleigh Barty of Australia after she defeated Germany's Andrea Petkovic 6-3, 6-1.

Qualifier Aliona Bolsova Zadoinov negotiated three rounds before the main draw began.

The 137th-ranked Spaniard continued to impress with a straight sets 6-2, 7-5 win against Russian Ekaterina Alexandrova.

Next up for Bolsova Zadoinov is American 17-year-old Amanda Anisimova, who extended her stay in Paris with a 7-6, 6-4 victory against Romania's Irina-Camelia Begu.

Romania's Simona Halep dropped just three games as she eased past Ukrainian Lesia Tsurenko 6-2, 6-1 into round four.

The third seed next plays Poland's Iga Świątek after she defeated Puerto Rico's Monica Puig 0-6, 6-3, 6-3.

Serbian world number one Novak Djokovic had a comfortable passage into round four as he beat Italian Salvatore Caruso 6-3, 6-3, 6-2.

Jan-Lennard Struff of Germany awaits after a gruelling victory against Croatian Borna Ćorić.

The German outlasted 13th seed Ćorić in a marathon five-set contest to win 4-6, 6-1, 4-6, 7-6, 11-9 in 4 hours 11min. 

Fifth seed Alex Zverev of Germany also took five sets to reach the second week at Roland Garros.

After going two sets up against Dusan Lajovic, Zverev lost his way and allowed the Serbian to level the match.

He regained his composure in the deciding set to record a 6-4, 6-2, 4-6, 1-6, 6-2 victory.

Zverev plays Italian ninth seed Fabio Fognini next after he won 7-6, 6-4, 4-6, 6-1 against Spaniard Roberto Bautista Agut.

Greek sixth seed Stefanos Tsitsipas overcame Filip Krajinović of Serbia 7-5, 6-3, 6-7, 7-6.

He will meet Switzerland's Stan Wawrinka, who edged out Bulgarian Grigor Dimitrov 7-6, 7-6, 7-6.

Gael Monfils won an all-French battle against Antoine Hoang 6-3, 6-2, 6-3.

His prize is a testing last-16 clash with Austrian Dominic Thiem after the fourth seed won 6-3, 4-6, 6-2, 7-5 against Argentina's Pablo Cuevas.

Juan Martin del Potro progressed with a 6-4, 6-4, 6-0 win against Australia's Jordan Thompson.

A fourth-round clash with 10th seed Karen Kachenov beckons as the Russian eased to victory 6-1, 6-3, 6-4 to knock Slovakia's Martin Kližan out.