In men's action, nine-time champion Rafael Nadal and defending champion Novak Djokovic both won in straight sets to reach the quarterfinals in Paris for the 11th time, equaling Roger Federer's record for the professional era. Next up: Nadal vs. No. 20 Pablo Carreno Busta, and Djokovic vs. No. 6 Dominic Thiem, with the winners facing off in the semifinals.
Heading into the French Open, many figured the women's draw was wide open, because of the absences of Williams' sister, Serena (who is pregnant), and Maria Sharapova (who was denied a wild-card entry that she needed as she comes off a drug suspension).
How right those folks were.
This was Muguruza's first attempt at defending a Grand Slam championship, and she ran into a determined Mladenovic, who was backed by a vocal crowd of countrymen who chanted her nickname, Kiki, throughout the match. Mladenovic often played to the fans, waving her arms to ask for more noise.
"I'm playing at home. Obviously they are excited. The atmosphere was just, yeah, amazing," Mladenovic said.
When Muguruza's complaints about the crowd were relayed to Mladenovic, she said she thought it was just as tough on her, because she had to deal with the burden of thousands counting on her to win.
"I don't think that they crossed the line," Mladenovic said. "Honestly, no, I don't think it was unsportsmanship or unfair or anything."
The last woman representing France to win the country's Grand Slam tournament was Mary Pierce in 2000. The 24-year-old Mladenovic never had been past the third round at her home major — and has never made it beyond the quarterfinals at any other.
But she managed to pull off the biggest victory of her career despite 16 double-faults, seven in each of the last two sets on a windy day with the temperature in the 60s (teens Celsius).
"Everything wasn't perfect. There were a few concerns," Mladenovic said, before joking: "I made about 35 double-faults today, but everything's OK!"
Muguruza, who was seeded No. 4 in Paris, beat Serena Williams in the French Open final last year. She also was the runner-up to the American at Wimbledon in 2015.
But the Spaniard has been repeatedly answering questions recently about whether expectations are different now that she is a major champion and whether that sort of pressure might affect her on court.
"I obviously was a little bit nervous," Muguruza said. "Through the match, I was getting more and more."
_
Follow Howard Fendrich on Twitter at http://twitter.com/HowardFendrich
_
More AP tennis coverage: https://apnews.com/tag/apf-Tennis