Eugenie Bouchard and Peng Shuai have both withdrawn from the inaugural WTA event in Hong Kong next week.
Bouchard would have been the top seed at the tournament, and Peng the top Chinese attraction following her semifinal run at the U.S. Open.
Bouchard, who was treated for illness during her fourth-round U.S. Open defeat, was quoted in a tournament statement as saying, "I had been very much looking forward to it, but unfortunately my medical team has advised me that I need to take the next two weeks off from competition to rest and recover after a very long season."
Peng retired from her semifinal against Caroline Wozniacki with what officials described as heat illness.
Tournament organizers said Peng will attend the event to fulfill her publicity obligations.
Sabine Lisicki has taken a wild card into the tournament.