Cibulkova came out like a house on fire - she stormed through the first set and broke early in the second set, eventually building a 61 20 lead. Just like in her first round match against Pemra Ozgen, she had a slight hiccup - Hsieh won two games in a row to make it 2-2 - but just like in that first round match, the No.1-seeded Slovak bounced right back, winning four games in a row to end it, 61 62.
There was some drama right at the end of the match though - serving for the match at 5-2, Cibulkova needed nine match points to finally close a stubborn Hsieh out in a marathon eight-deuce final game.
"I have to say I was playing much better today than I did yesterday," Cibulkova said. "It was quite a good match from my side. I was feeling the ball well today. I didn't let her take me out of my rhythm."
Cibulkova had been tied for WTA-level match win leader for the year with Li and Radwanska at 21, but is now the standalone leader. And with three more rounds potentially, she could go as high as 25 here.
Awaiting Cibulkova in the quarterfinals will be No.6 seed Zarina Diyas, who won her second round match on Wednesday. Cibulkova and Diyas have never played, but Diyas did win her only previous match against a Top 10 player - she beat a No.7-ranked Jelena Jankovic at Moscow in 2011, 61 62.
"I've never played her before and I've never seen her playing, but I know she's playing quite well," Cibulkova said of Diyas. "But she's an up-and-coming player and players like that play with nothing to lose, they play quite free, so it's going to be another good test for me. I'll have to be focused."
The other three seeds in action - No.2 seed Zhang Shuai, No.3 seed Karolina Pliskova and No.7 seed Donna Vekic, all advanced to the quarterfinals as well, as did Cagla Buyukakcay, who scored a 64 64 win over Tadeja Majeric to become the first Turkish player in history to reach a WTA quarterfinal.
"I'm so happy!" Buyukakcay said. "I am really proud to become the first Turkish quarterfinalist at a WTA tournament. I've been working so hard and my goal was to keep improving my results this year.
"Hopefully I can keep this level up throughout the season."