Johanna Konta's participation in the WTA Finals in Singapore may come under threat following her withdrawal from the Hong Kong Open on Thursday, while Venus Williams was surprisingly knocked out.
The Briton, seeded third for the WTA International event at Victoria Park, had been set to face Wang Qiang, but pulled out due to an abdominal injury, handing the Chinese qualifier a walkover and passage to the third round.
Konta sits eighth on the Road to Singapore leaderboard, occupying the final qualifying berth for the end-of-season showpiece, and could yet find herself ousted by Dominika Cibulkova, Carla Suarez Navarro or Svetlana Kuznetsova.
"Obviously it's never the ideal way to finish a tournament, and definitely never the intention when you come to play," she said.
"I really enjoy playing here in Hong Kong and I was really looking forward to making this week last as long as possible.
"Unfortunately it wasn't as long as I would have liked but I need to look after my body first - I've only got one - so I really have to make sure I make the right decisions for my health.
"I'm looking forward to hopefully coming back next year and making it a full week here."
Having benefited from Konta's departure, Wang will now face Caroline Wozniacki in the quarter-finals, the Danish fifth seed getting the better of Britain's Heather Watson 6-3 6-3.
Having seen her match interrupted by rain on Wednesday, world number one Angelique Kerber, last year's runner-up in Hong Kong, completed a 6-2 3-6 6-2 victory over Louisa Chirico a day later.
Next up for the German is Australian eighth seed Daria Gavrilova, who accounted for Katerina Siniakova in straight sets.
Veteran American Williams was a major casualty, Alize Cornet beating the second seed 6-2 3-6 6-2.
Bethanie Mattek-Sands came from a set down to beat sixth seed Caroline Garcia 4-6 6-2 6-4, while Kristina Mladenovic ousted Nao Hibino in straight sets.