Second-seeded Petra Kvitova was beaten by Sara Errani in the first round of the China Open in Beijing on Sunday.
The unseeded Italian won in straight sets against the Czech 7-5, 6-4 in just over two hours, while Romanian top seed Simona Halep retired injured when 5-4 down against Spain's Lara Arruabarrena Vecino.
Polish fourth seed Agnieszka Radwanska got through to the next round when her American opponent CoCo Vandeweghe was forced to retire injured with the score at 6-3, 0-0.
In other first round matches, 16th seeded Elina Svitolina from Ukraine beat Kazakhstan's Yulia Putintseva 7-5, 6-2 and France's Caroline Garcia got past local player beat Zheng Saisai of China 6-2, 6-2.
Colombian Mariana Duque had a straight sets win over Tsvetana Pironkova of Bulgaria, winning 6-3, 6-3, and America's Bethanie Mattek-Sands beat France's Alize Cornet 6-3, 6-3.
Denmark's eighth seed Caroline Wozniacki cruised past Bojana Jovanovski of Serbia 6-2, 6-4.