(CNN) -- Fourth seed Elena Dementieva followed third-ranked Venus Williams in departing the French Open at the third-round stage after being upset by Samantha Stosur on Saturday.
Samantha Stosur celebrates after upsetting Elena Dementieva at Roland Garros.
The 30th-seeded Australian won 6-3 4-6 6-1 to equal her best performance at a Grand Slam tournament.
The 25-year-old Stosur will next face Virginie Razzano for a place in the quarterfinals, with the unseeded Frenchwoman later beating Italy's Tathiana Garbin 7-5 7-5.
Stosur lost to Olympic champion Dementieva in the third round of the Australian Open this year, but this time was able to avenge her compatriot Jelena Dokic -- who was on top of the Russian in the previous round before pulling out with a back injury.
The Serbia-born Dokic was the last Australian woman to reach the last eight at Roland Garros in 2002.
Dementieva, the runner-up in Paris in 2004, admitted afterwards that she is not playing well and had struggled on the energy-sapping clay.
"I just feel I'm far away from being in good shape. I feel like I couldn't perform any better," the 27-year-old told reporters. "She was playing very solid, very good first serve. Just too many unforced errors and not enough power from me. I did what I could."
"I'm going to take two days off and then just try to work on my physical condition and make sure that I'm going to be ready to move in the right direction on the grass court, because it's very special. I'm just trying to get ready for Wimbledon."
Second seed Serena Williams booked a last-16 clash with Canadian 24th seed Aleksandra Wozniak, battling past unseeded Spaniard Maria Jose Martinez Sanchez in a 4-6 6-3 6-4 win marred by uncharacteristic unforced errors.
Wozniak had earlier defeated Lourdes Dominguez, also of Spain, 6-2 3-6 6-3
Fifth seed Jelena Jankovic reached the fourth round with a comfortable 6-1 6-1 win over unseeded Australian.
The Serbian will face either Danish 10th seed Caroline Wozniacki or unseeded Romanian Sorana Cirstea for a place in the quarterfinals.
Seventh seed Svetlana Kuznetsova cruised into the last 16 with a 6-1 6-3 crushing of unseeded Hungarian Melinda Czink.
The Russian, runner-up in 2006, will next play 12th seed Agnieszka Radwanska after the Pole disposed of Ukraine's Kateryna Bondarenko 6-2 6-4.
Ninth seed Victoria Azarenka of Belarus beat Spanish 22nd seed Carla Suarez Navarro 5-7 7-5 6-2 and will next take on defending champion Ana Ivanovic.