By Erik Gudris | Sunday, October 4, 2015

Both Simona Halep and Petra Kvitova found themselves exiting the China Open in Beijing after their opening round matches. That means the last WTA Premier Mandatory event of the season will go on without its two top seeds.

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Top seed Halep retired due to a left ankle injury in her match against Spain's Lara Arruabarrena. After falling behind 5-4 in the opening set, Halep decided she could not go on.

"I have pain in my Achilles. It's getting worse," Halep said to WTA.com. "I thought that it was getting better and I could play, but no - I don't want to force it. And it's a tough injury because it's always dangerous to continue with the tendon, so, I hope to just recover and be healthy again soon."

Halep hopes to be better in time for the upcoming year-end championships in Singapore.

"I hope I can play. It was my goal this year. I will see - I need treatment and a break, for sure."

No. 2 seed and last year's finalist Kvitova entered her opening round match against Sara Errani with a perfect 6-0 record against the Italian.

Yet it was Errani who played inspired tennis throughout as she handled Kvitova's serve and pace with accurate returns and thoughtful play up at net.

After Errani took the opening set, both women traded service breaks throughout the second set. Errani earned another service break to go up 5-4. She didn't look back as she closed out the upset win 7-5, 6-4. It's Errani's third career top five win.

"I had never beaten her, and she's a really good player, so I'm happy I could finally win in a big tournament like this one," Errani said. "It was just a few points that made the difference. I just tried to stay there every point and stay solid without too many mistakes - that's my game, anyway."

The WTA Premier Mandatory now finds itself without its top two seeds after the earlier withdrawals from both Serena Williams and last year's winner Maria Sharapova.

No. 3 seed Flavia Pennetta won her first match since claiming the US Open title last month. Pennetta outlasted Chinese wildcard Xinyun Han 7-5, 4-6, 6-4.

Sloane Stephens upset No. 9 seed Karolina Pliskova 6-3, 6-2.

(Photo Credit: Getty Images)