GUANGZHOU - Puerto Rico's Monica Puig upset number two seed Andrea Petkovic of Germany in first-round play Tuesday in the WTA Guangzhou International Women's Open.

The unseeded Puig defeated Petkovic 6-1, 6-4 in the biggest upset of the day in the southern Chinese city. Players are battling for prize money of $250,000. There were no surprises for top-seeded Simona Halep of Romania, who beat Petra Martic of Croatia 6-4, 6-2.

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 the day's other upset, Bojana Jovanovski of Serbia defeated number seven seed Danka Kovinic of Montenegro 6-4, 6-2. Number three seed Sara Errani of Italy, meanwhile, was pushed to three sets before defeating China's Duan Ying-Ying 6-3, 3-6, 6-2.

Fourth seed Jelena Jankovic of Serbia beat Russia's Elena Vesnina 7-6 (7/3), 6-3, taking the first set with a tiebreaker. Svetlana Kuznetsova of Russia, seeded fifth, defeated Slovakia's Daniela Hantuchova 6-4, 7-5 Sixth seed Monica Niculescu of Romania beat Kazakhstan's Yulia Putintseva 7-6 (7/5), 1-6, 6-3, needing a tiebreaker to win the first set.

And China's top player Zheng Saisai, seeded eighth in the tournament, downed Aleksandra Krunic of Serbia 6-2, 6-1.