Russia's Elena Dementieva became the latest high-profile casualty at the Pan Pacific Open, when the third seed was upset by Ukraine's Kateryna Bondarenko in the second round on Tuesday.
The Olympic champion was beaten 6-2, 6-7, 6-1 to leave the $2 million Tokyo event shorn of its top three seeds. Fourth seeded Caroline Wozniacki followed the Russian, who had to retire with a viral infection.
Former world number one Maria Sharapova had no such problems, however, powering into the last 16 in Tokyo with an almost flawless 6-0, 6-1 victory over Australia's Samantha Stosur.
Current number one Dinara Safina, second seed Venus Williams and French Open champion Svetlana Kuznetsova all lost their opening matches on Monday after first-round byes.
Dementieva blamed some questionable line calls and fatigue for her loss to a player she had not conceded a set to in four previous meetings.
BAD CALLS
"There were way too many bad calls from the chair umpire today," she grumbled.
"I'm surprised they don't have a challenge system at such a big event," she added.
Dementieva, who was ousted in the second-round of the US Open earlier this month, added: "I played way too many matches in the US Open series. I just didn't have the energy."
Sharapova, 25th in the world rankings following shoulder surgery a year ago, answered the prayers of tournament organisers by overpowering 12th seed Stosur in just 57 minutes.
Stosur at least avoided the dreaded "double bagel" by saving two match points at 0-5 in the second set but the Russian wrapped up a clinical victory with an ace two minutes later.
"I just want to finish the year on a good note," Sharapova said. "I served smart. It was definitely a good day at the office all around."
Sharapova next faces countrywoman Alisa Kleybanova, who knocked out sixth seed Vera Zvonareva 3-6, 6-4, 6-2 in another Russian clash.
Beaten US Open finalist Wozniacki walked off court in obvious discomfort after losing the first five games of her match against Canada's Aleksandra Wozniak.
