World number one Serena Williams and number six Agnieszka Radwanska were dumped out of the $2.4 million WTA Wuhan Open.
Williams retired hurt while leading 6-5 in the opening set against France's Alize Cornet while Radwanska was beaten by a determined Caroline Garcia in a hard-fought three-set battle.
Cornet, who arrived in Wuhan with her confidence high after reaching the final at the WTA Guangzhou Open on Saturday, had beaten Williams twice this year, handing the American power-hitter her earliest defeat at Wimbledon for nine years in June, and also winning at Dubai in February.
The reason for the retirement was not immediately clear.
The tournament's top two seeds were eliminated within hours, with Garbine Muguruza of Spain beating Simona Halep of Romania 2-6, 6-2, 6-3.
Muguruza, who beat Williams at the French Open, dropped the first set in 35 minutes but rallied to win the first four games of the second set and the last four games of the third.
Elsewhere, Caroline Wozniacki continued her revival with a 6-1, 3-6, 7-6 win over Carla Suarez Navarro.
Coco Vandeweghe beat Jelena Jankovic 4-1 (Jankovic retired)
Karolina Pliskova beat Andrea Petkovic 6-4 6-4
Garbine Muguruza Blanco beat Simona Halep 2-6 6-2 6-3
Alison Riske beat Sara Errani 6-4 6-4
Elina Svitolina beat Sabine Lisicki 7-6 6-3
Timea Bacsinszky beat Ekaterina Makarova 6-4 6-1