GUANGZHOU, China – 23-year-old Swiss Viktorija Golubic is into the quarterfinals at the Guangzhou International Women’s Open after coming back from a set down to upset top seed Sara Errani, 6-7(7), 6-3 6-4.

Aside from reaching her fourth quarterfinal this year in what has become her breakthrough season, Golubic has also avenged her Bastad loss to Errani, where she lost to the Italian after taking her to a first-set tiebreaker.

“I’m very, very tired, it was such an exhausting match,” Golubic said. “We played each other on clay this year, and that was also very tough so I was prepared for that.”

“But still in the end I had to put all the energy together to come through, and I am very happy.”

Golubic held a 5-3 lead in the first set, as well as five set points in the tiebreak during a tight opening set. Errani fought off Golubic’s chances with her tricky forehand slices and dogged defense, roaring back from 2-6 down in the tiebreak to take the first set. Golubic stayed aggressive, and took advantage of Errani’s vulnerable serve to create more chances, outlasting the Italian after a three-hour marathon to advance to the quarterfinals.

“Sara is a very tricky player – she makes you think and she gives you the balls back, a very tough player,” Golubic said. “I was doing many good points, but I also missed a lot.”

“I tried to find the balance between aggressiveness and consistency, and it was hard work to do.”

Sabine Lisicki is also through to the quarterfinals after a 6-4, 6-1 victory over Chinese wildcard Peng Shuai.

Despite the match being a mostly one-sided affair during the hour-and-six-minute encounter, Lisicki admitted it was difficult to take on her good friend.

“It’s always so tough to play a friend,” Lisicki said in post-match press. “Shuai and I have played doubles together a few times, so we know each other quite well.”

“I thought I played very well. I knew that I had to play well and strong to beat her. I’m very happy with my game, but also wish her the best in her comeback.”

Joining Golubic and Lisicki in the quarterfinals at the Guangzhou International Women’s Open is No.3 seed Ana Konjuh, who weathered a late challenge from Georgian qualifier Sofia Shapatava to advance 6-1, 7-6(2).

“I’ve never played her before but I know her from Fed Cup, so I’ve seen her playing,” Konjuh said of her opponent. “I just had a tactic and just focused on myself more.

“In the second set she came back and fought for every point, so it was a bit harder.”

No.2 seed Jelena Jankovic also advanced in Guangzhou after Rebecca Peterson was forced to retire with a right thigh injury after trailing 6-1, 1-0.