LINZ, Austria - No.5 seed Sorana Cirstea returned to the quarterfinals at the Upper Austria Ladies' Linz for the first time in six years on Thursday, edging Russian Natalia Vikhlyantseva, 7-6(14), 6-4 in Thursday's final match.

"It was a tough, tough match. We played over two hours for two sets. She played at a very high level, and I'm happy I managed to find a way, to fight," Cirstea said after the match. "I think this is a big step forward for get the win when I'm not playing my best tennis."

In a mammoth opening set that lasted 80 minutes, and a tiebreak which took 20 on its own, Cirstea saved five set points overall and took a one-set lead on her sixth chance. 

After seeing seven break points go by in Vikhlyantseva's first two service games, Cirstea found herself behind as she became the first player to surrender her serve in the seventh game.

The No.5 seed hit back immediately, winning four straight points from 30-0 down to finally break through on the Russian's delivery before the set wound through to its dramatic conclusion. 

"I think, no, I'm sure that this was the longest tiebreak of my life," Cirstea said. "At some point, I didn't even know the score anymore. I just knew if I was one point ahead, or if she was one point ahead...I think for me it was very important to not focus on the score."

Neither player could build a lead of more than a point until Vikhlyantseva secured a 6-4 lead, but saw herself both unable to convert on five set points, and save five of Cirstea's chances, before evenutally succumbing in the set.

"It just felt like forever, that the whole match was a tiebreak. I ran a lot today, and it's good that I play late again tomorrow so I have time to rest and recover."

- Sorana Cirstea on her mammoth opening set

With momentum on her side, the Romanian built a double break advantage in the second set by winning four of the first five games.

Though Vikhlyantseva hit back to pull closer, she was unable to level the set as Cirstea moved on in two hours, 11 minutes.

After No.7 seed Tatjana Maria won her second round yesterday, Cirstea made sure that four seeds would feature in Friday's quarterfinal matches.

Top seed Magdalena Rybarikova in action in Linz. (Matthias Hauer/GEPA)

No.1 seed Magdalena Rybarikova and No.2 seed Barbora Strycova also progressed to the quarterfinals in contrasting fashion on Thursday afternoon, as two of just three seeded players to advance to the last eight.

To open Thursday's play, No.2 seed Strycova was tested by 20-year-old qualifier Jana Fett of Croatia, but prevailed in three sets, 2-6, 6-3, 6-3. 

With the match level at one set apiece, the Czech played the big points in perfect fashion, converting on her lone break point opportunity in the deciding set and saving all five that she faced. 

Top seed Rybarikova had a straight sets path through to the last eight, as she defeated Germany's Carina Witthoeft, 7-6(4), 6-3.

Johanna Larsson also reached the quarterfinals in Linz. (Matthias Hauer/GEPA)

The Slovak and German combined for 12 straight holds in the opening set, as Rybarikova faced the only break point in the sixth game, and the top seed edged ahead as she won four of the last five points in the tiebreak from the 3-3 change of ends. 

The Wimbledon semifinalist did not have the match entirely her own way despite winning in straight sets, as she was twice forced to come from a break down in the second set before winning the last four games of the match. 

The seeded trio were joined in the quarterfinals by Viktorija Golubic and Johanna Larsson, who defeated Bulgarian qualifier Viktoriya Tomova and American Varvara Lepchenko, respectively. 

Last year's finalist in Linz who finished runner-up to Dominika Cibulkova, the Swiss came from a set down to earn her first win against the 22-year-old Tomova, while Larsson earned a spot in just her second quarterfinal of the season.