Denisa Allertova of the Czech Republic defeated top seed Simona Halep in straight sets in quarterfinal play Thursday in the WTA Guangzhou International Women`s Open.
Unseeded Allertova pulled off the biggest upset of the tournament so far, beating the Romanian 6-4, 6-3.
Halep, ranked number two in the world, was defeated in the semifinals of the US Open this month by eventual champion Flavia Pennetta of Italy.
In another upset, unseeded Yanina Wickmayer of Belgium defeated Romania`s Monica Niculescu, the number six seed, 6-2, 6-2.
Sara Errani, seeded third, overwhelmed number eight seed Zheng Saisai, China`s top player, 6-1, 6-0, leaving no more Chinese singles players in the event.
And in the only battle of seeded players, Jelena Jankovic of Serbia, number four, defeated fifth seed Svetlana Kuznetsova of Russia, 6-2, 7-5.
Players are battling for prize money of $250,000.