Toronto - Maria Sharapova had an upset loss to 135th-ranked Galina Voskoboeva of Kazakhstan at the Rogers Cup on Thursday, becoming the latest casualty of a draw which has lost 11 of the 16 seeds.
The 26-year-old Voskoboeva, who ousted Marion Bartoli and Flavia Pennetta to reach the third round, beat fifth-seeded Sharapova 6-3, 7-5 with soft drop shots and had the veteran chasing balls to the baseline throughout the match.
"It makes for an exciting story because at the end of the day it doesn't matter what you're ranked or seeded, the reason we go out and play the matches is to know who's going to be the winner on that day," said Sharapova, who has 23 career singles titles. Voskoboeva reached her first career semifinal earlier this year.
"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," Sharapova added.
Hours earlier, No 6-seeded Li Na lost 6-2, 6-4 to No 10 Samantha Stosur of Australia. Li became the first Asian player to win a Grand Slam singles title two months ago at the French Open.
No. 11 Andrea Petkovic of Germany also reached the quarterfinals after cruising by Wimbledon champion Petra Kvitova of the Czech Republic 6-1, 6-2.
Third-seeded Vera Zvonareva of Russia is also out, losing 6-4, 7-6 (4) to Agnieszka Radwanska of Poland.
Serena Williams advanced with a 4-6, 6-3, 6-3 win over Chinese qualifier Zheng Jie, taking momentum in the second and dictating play from there.
"I decided that I had to really relax and really calm down and just try to start playing better," Williams said. "She was really just playing well from the whole match. I just tried to do better."
Williams will face Lucie Safarova next. The Czech downed eighth seed Francesca Schiavone of Italy 6-3, 6-3.
Voskoboeva and Sharapova battled point for point before the Kazakh player nearly lost her composure, allowing Sharapova an opening in the match that lasted 1 hour, 47 minutes.
The 24-year-old Sharapova was facing match point three times but Voskoboeva double-faulted twice and then fired a shot into the net. Voskoboeva hurled her racket to the ground in frustration a couple of times pulling herself together, sealing the victory when Sharapova's shot fell short.
"Obviously she played really well this tournament and you could tell today(Thursday) that she came to the match with a lot of confidence, swinging away and going for serve and her shots," Sharapova said. "If she could consistently play like that, she wouldn't be ranked where she is today. She showed that she can play really great tennis."
Fourth-seeded Victoria Azarenka of Belarus booked her spot in the quarterfinals with a 6-1, 6-2 win over Maria Jose Martinez Sanchez of Spain, while Roberta Vinci of Italy - who eliminated top-seeded Caroline Wozniacki the previous day - defeated Ana Ivanovic of Serbia, 7-6 (3), 6-2.
Thursday's loss of star power followed the ousting of Wozniacki, second-seeded Kim Clijsters, who withdrew earlier this week due to an abdominal injury, and former world No. 1 Jelena Jankovic and No 9 Bartoli.
Li was playing her first game of the week after being handed a bye through the first round and then a walkover victory when compatriot Shuai Peng withdrew with an injury.
She fired numerous returns long on another blustery day at Rexall Centre, eventually bowing out when she smacked a forehand into the net.
The match was held during a power outage at the venue - a Toronto Hydro problem, according to Rogers Cup organisers. The main scoreboard stayed dark for just over an hour, while the corner scoreboard periodically worked, powered by a backup generator.
"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," Li 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."