Justine Henin needed three hours to beat Slovenian qualifier Katarina Srebotnik and preserve her unbeaten record at the Dubai Championships.
The top-seeded Belgian surrendered a tense second set before closing out a 7-5 6-7 (6-8) 6-3 victory.
"That's the kind of match I need," said Henin after making the quarter-finals.
"It's never easy to have a bye and play a girl that has played a few matches. In the third set I felt the best I've felt in the last few weeks."
Third-seeded Serb Ana Ivanovic showed no sign of her recent ankle injury as she defeated Czech Nicole Vaidisova 6-4 6-0.
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And Amelie Mauresmo will meet second seed Svetlana Kuznetsova in the quarter-finals after beating Japan's Akiko Morigami 4-6 6-1 6-4 in Dubai.
Mauresmo, who has slipped to 29th in the world rankings, is looking to reach her first semi-final since June but she faces a tough test against Kuznetsova.
The Russian world number two thrashed Lucie Safarova 6-1 6-2.
"Despite her playing well and hitting the ball very solid I was also just struggling with my game"
Fourth seed Jelena Jankovic needed more than two hours to see off India's Sania Mirza 4-6 6-3 6-4.
Mirza led 3-1 in the final set and had three points to make it 5-3 before Jankovic prevailed.
"She gave me a hard time on the court," said Jankovic.
"Despite her playing well and hitting the ball very solid I was also just struggling with my game."
The Serb now meets Anna Chakvetadze, who beat compatriot Dinara Safina 6-7 6-4 6-3.
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