Wuhan - Top-ranked Garbine Muguruza advanced to the third round of the Wuhan Open by beating Lesia Tsurenko 6-4, 6-4 on Tuesday.
The Wimbledon champion from Spain broke her opponent early in each set.
She will next face Magda Linette of Poland.
"Two years ago I left here in the final. I always play well in China," said Muguruza, who lost to Venus Williams in the 2015 championship match. "I will try to just keep going forward."
In a pair of upsets, second-ranked Simona Halep and fourth-seeded Caroline Wozniacki both lost.
Halep lost to Daria Kasatkina 6-2, 6-1, meanwhile Wozniacki, who won in Tokyo last weekend, was beaten by qualifier Maria Sakkari of Greece 7-5, 6-3.
It was Kasatkina's third win over a top-five player. She beat then-No 1 Angelique Kerber twice this year.
"The game was much more difficult than the score is," Kasatkina said.
Halep came into the tournament with a chance to take over as No 1 from Muguruza this week.
Fourth-ranked Karolina Pliskova kept alive her shot at No 1 by beating Shuai Zhang 6-4, 3-6, 6-4. To regain the top ranking, Pliskova must win the Wuhan Open title and hope Muguruza loses before the semi-finals.
"I always want to play better than I did last year," Pliskova said. "I already won one round so hopefully I can win one more."
Also, two-time major champion Svetlana Kuznetsova lost to Alize Cornet of France 6-3, 6-3, while seventh-seeded Dominika Cibulkova, eighth-seeded Jelena Ostapenko, ninth-seeded Agnieszka Radwanska and 16th-seeded Elena Vesnina all won.
Other winners included Linette, Ekaterina Makarova, Caroline Garcia, Wang Qiang, Monica Puig and Varvara Lepchenko.
Results of singles matches from the WTA Wuhan Open on Tuesday (x denotes seeding):
Garbine Muguruza (ESP x1) bt Lesya Tsurenko (UKR) 6-4, 6-4
Magda Linette (POL) bt Katerina Siniakova (CZE) 6-1, 6-2
Monica Puig (PUR) bt Peng Shuai (CHN) 4-6, 6-3, 6-4
Jelena Ostapenko (LAT x8) bt Barbora Zahlavova Strycova (CZE) 2-6, 7-5, 6-3
Karolina Pliskova (CZE x3) bt Zhang Shuai (CHN) 6-4, 3-6, 6-4
Wang Qiang (CHN) bt Sorana Cirstea (ROM) 6-3, 6-3
Agnieszka Radwanska (POL x9) bt Julia Gorges (GER) 7-5, 7-5
Alize Cornet (FRA) bt Svetlana Kuznetsova (RUS x6) 6-3, 6-3
Varvara Lepchenko (USA) bt Kiki Bertens (NED) 6-4, 6-4
Elena Vesnina (RUS x16) bt Elise Mertens (BEL) 6-2, 6-4
Maria Sakkari (GRE) bt Caroline Wozniacki (DEN x4) 7-5, 6-3
Dominika Cibulkova (SVK x7) bt Jil Teichmann (SUI) 6-2, 6-2
Caroline Garcia (FRA) bt Christina McHale (USA) 6-1, 6-1
Ekaterina Makarova (RUS) bt Lauren Davis (USA) 6-2, 6-4
Darya Kasatkina (RUS) bt Simona Halep (ROM x2) 6-2, 6-1