Top seed Justine Henin shrugged off a determined challenge from Australia's Alicia Molik to reach the quarter-finals of the Qatar Open on Wednesday.

World No.2 Henin, bidding for a 'Gulf double' after her triumph in Dubai last week, won the first set with ease.

But she inexplicably lost her focus in the second set and it was only thanks to Molik's unforced errors that the Belgian managed to wrap up the 90 minute-match 6-2 7-6 (11-9).

Henin blamed fatigue for her second-set wobble.

"You always expect a tough match against a player like Alicia. I had a good start... and then I lost my energy a little bit," Henin said.

"I lost some intensity in my game. And she gave me lots of trouble on her serve. I wasn't playing that well that time in the second set.

'But I came back and found everything. I didn't do my best, but I won in two sets. That is the key for me."

The Belgian was joined in the last eight by seeds Svetlana Kuznetsova, Patty Schnyder and Francesca Schiavone.

Fifth seed Schnyder's reward for a 6-3 6-4 win over Spain's Anabel Medina Garrigues was a date with Henin.

Kuznetsova, a 7-5 6-1 winner over Germany's Julia Georges, will next face Schiavone.

Schiavone, seeded eighth, was made to work hard in an all-Italian battle with Mara Santangelo before her opponent quit with a left wrist injury while trailing 4-6 7-6 1-0.

Henin said she was expecting a tough quarter-final outing against Schnyder.

"She really gave me a lot of trouble in the past. We are always involved in big fights, in three sets," Henin said.

"Last time she beat me in three sets in Charleston. She is a special player, unlike others as she is a lefty. It will be a tough one. I have to raise my level if I have to win."

Indian pin-up Sania Mirza, who suffered a knee injury during her first-round win, pulled out of her match against Katerina Bondarenko.

"I have a painful right knee and I didn't want to take any risk," Mirza said.

"I am flying back home (Hyderabad) and will have a scan tomorrow."

Brought to you by AAP © 2024 AAP