World number one Simona Halep struggled to shake off the effects of a back injury before being beaten 6-0 7-5 by Slovak Dominika Cibulkova in the second round of the Wuhan Open on Tuesday.
Halep, who injured herself in training earlier this week, offered some resistance in the second set after a bad start to the match but could not prevent an early exit in her first tournament since the US Open.
"It was tough to play in the beginning because my back was blocked. I knew it was, because we talked together with my team. Normally, I'd have to retire, but I didn't want to, and I don't like to do that. I pushed myself to play better," Halep said.
"I'm not disappointed, but I'm just sad this injury came from nowhere. I'm just going to go with the flow, and we'll see what's going to happen in a few days."
Up next for Cibulkova is Russia's Daria Kasatkina who saved four match points before overcoming Chinese 17-year-old Wang Xiyu 6-1 3-6 7-6(8).
Former world number one Karolina Pliskova was not as lucky against another local hope in Wang Qiang, who clinched a 6-1 3-6 6-3 victory in two hours and eight minutes.
Qualifier Katerina Siniakova, who was down a set and facing match point, produced a remarkable comeback to beat defending champion Caroline Garcia 3-6 7-6(5) 7-6(4).
Reigning Australian Open champion Caroline Wozniacki admitted to not being at her best yet despite powering past Rebecca Peterson 6-4 6-1 in 88 minutes.
"I was a little rusty, but I played a really good opponent today," Wozniacki, who has not made it past the second round of a tournament since winning the Eastbourne title in June, said.
Spaniard Garbine Muguruza also made short work of Viktorija Golubic, winning 6-0 6-1 while Petra Kvitova beat Aleksandra Krunic 6-3 6-4. (Reporting by Shrivathsa Sridhar in Bengaluru Editing by Christian Radnedge)