Wimbledon champion Petra Kvitova and French Open winner Li Na both crashed out of the Toronto WTA tournament on Thursday as the top seeds tumbled.
American Serena Williams avoided joining them after rallying from behind to beat Zheng Jie and win through to the quarter-finals.
Defeats for Kvitova and Li, who both lost in straight sets, mean eight of the top 10 seeds have now fallen.
Czech seventh seed Kvitova, 21, who recently recovered from a thigh injury, was beaten 6-1, 6-2 by Germany’s Andrea Petkovic. Sixth seed Li went out 6-2, 6-4 to Australian Samantha Stosur.
But the loss of star power didn’t end there in a bruising day on the hardcourts.
The pre-US Open tournament also saw fifth seed Maria Sharapova lose in straight sets, with the Russian going down 6-3, 7-5 to Kazakh qualifier Galina Voskoboeva — ranked 135th in the world.
“Whether you’re No.1 in the world or you’re facing someone that’s 100 or so, you still have to go out and win. That’s what the sport is all about,” said Sharapova, who has 23 career singles titles.
Williams advanced but not before receiving a first-set scare from Chinese qualifier Zheng Jie.
Williams used her powerful serve to come through, firing 10 aces in a 4-6, 6-3, 6-3 win.
“I decided that I had to like really relax and really calm down and just, you know, try to start playing better,” Williams said.
“She was really just playing well from the whole match. I just tried to do better.”
Third seed Vera Zvonareva of Russia was also knocked out, beaten 6-4, 7-6 (7/4) by Agnieszka Radwanska of Poland.
The big names join top-ranked Caroline Wozniacki on the sidelines after she was beaten Roberta Vinci on Wednesday.
Li, who was playing her first match of the week after a bye and a walkover, said she felt “like a junior on the court”.
The 29-year-old made sporting history at the French Open in June when she became the first player from an Asian country to win a Grand Slam singles title.
“It’s always tough after a break to come back for the first match, because I had six or seven weeks that I didn’t play a tournament,” she said.
“At the beginning of the match I didn’t even know what I should do on the court, not like during the clay-court season.”
Li bowed out at the Rexall Centre venue after 89 minutes with a forehand into the net.
“Today was so, so windy, I couldn’t use my serve a lot in the first serves,” Li said.
“If you watched the match, everyone can see, she has a huge, big serve. It’s tough for me to return.”
Voskoboeva, 26, had already breezed past Marion Bartoli and Flavia Pennetta before dispatching Sharapova.
The Kazakh beat the six-foot-two-inch (1.88 metre) Russian with perfectly timed drop shots, running her around the court in the one hour, 47 minute contest.
In other matches, fourth seed Victoria Azarenka of Belarus booked her spot in the quarter-finals with a 6-1, 6-2 win over Maria Jose Martinez Sanchez of Spain, while Roberta Vinci of Italy defeated Ana Ivanovic of Serbia, 7-6 (7/3), 6-2.
