No. 9-seeded Venus Williams lost to eighth-seeded Timea Bacsinszky of Switzerland 6-2, 6-4.
Venus Williams, a seven-time major champion, took a 2-0 lead before dropping eight games in a row. She managed to produce only six winners in the match while committing 24 unforced errors.
Men's No. 1 Novak Djokovic wrapped up a rain-interrupted victory with little trouble to reach the quarterfinals as he pursues his first French Open title.
Djokovic, trying to win a fourth consecutive major trophy and complete a career Grand Slam, needed only 71 minutes Wednesday to finish off No. 14 Roberto Bautista Agut of Spain 3-6, 6-4, 6-1, 7-5. The match was suspended because of rain Tuesday, with Djokovic leading 4-1 in the third set.
With his fourth-round win, Djokovic became the first man to break the $100 million mark in prize money.
"With my coaching team, we had some tough talks on Tuesday night," Djokovic said. "But I came back today with more intensity even though it was a tough mental and physical battle."
Serena Williams' match originally was scheduled for Monday, but showers forced cancellation of an entire day of play at Roland Garros for the first time in 16 years. More rain followed on Tuesday and allowed only two hours of play, sending the fourth-round matches on the top half of the women's draw to be pushed back again.
Williams hit 27 winners in her 62 minutes on court.
"I think it's definitely a whole new ballgame," Williams said. "I didn't play my best in the third round and I really wanted to come out and do a lot better and prove that I can do better than that."
Williams, who remains on track to become the first player to defend the title in Paris 2007, is now just three wins away from her 22nd major title, matching Steffi Graf's total and closing in on Margaret Court's all-time record of 24.
Afterwards, Williams refused to be drawn on her relentless record-chasing exploits.
"I think every day, for me, is important to get up for all my matches, you know, first round to the last round," Williams said. "I feel like the moment I step on the court that's all I see, is the ball and, you know, the opportunity to do the best I can."
Williams will face unseeded Yulia Putintseva of Kazakhstan in the quarterfinals, the first of a potential four matches in four days.
"Four in a row? When we play regular tournaments you play four, five matches in a row. It's what happens," Williams said. "It's something you just get used to. It's totally fine I think for me and for everyone."
Putintseva scored a rain-delayed 7-5, 7-5 win over No. 12 seed Carla Suarez Navarro of Spain.
Kiki Bertens of the Netherlands reached her first Grand Slam quarterfinal by beating 15th-seeded Madison Keys of the United States 7-6 (4), 6-3.
Dominic Thiem of Austria, who reached his first Grand Slam quarterfinal by beating Marcel Granollers of Spain 6-2, 6-7 (2), 6-1, 6-4.
Thiem will face 12th-seeded David Goffin of Belgium, who completed another rain-interrupted fourth-round match with a 4-6, 6-2, 6-2, 6-3 win over Ernests Gulbis of Latvia.