Victoria Azarenka withdrew after injuring her hip ©Getty Images

Injuries forced defending champion Petra Kvitová and ex-world number one Victoria Azarenka to withdraw from the Qatar Open, on what was otherwise a routine day for the top seeds.

Elise Mertens benefited as Czech player Kvitová could not continue after an injury to her left wrist and withdrew when a set down.

Mertens will now face fourth seed Anett Kontaveit of Estonia in the round of 16.

Kvitova had won the Qatar Open in 2018 and 2021, beating Garbiñe Muguruza in the final on both occasions.

Azarenka joined Kvitova on the sidelines after hip pain forced her to withdraw before her clash against American Madison Brengle.

With world number one Ashleigh Barty from Australia not playing because of injury, world number two Aryna Sabalenka is the top seed and the Belarusian lived up to the tag as she breezed past France's Alizé Cornet 6-2, 6-2.

"It definitely wasn't easy," Sabalenka said after the victory. 

"It was a really tough match. 

"She played really well, she pushed me a lot.

"I expected long rallies in this match and I prepared myself for this kind of rallies. 

"The tactic was just to stay in the point as long as I can, push her as much as I can, and to serve well."

Czech Barbora Krejčíková, the world number three, set up a rematch from last month's Australian Open with Latvia's Jelena Ostapenko after she demolished Poland's Magda Linette 6-1, 6-3

American teenager Coco Gauff defeated France's Caroline Garcia 6-2, 7-6 to set up a last-16 meeting with Spaniard Paula Badosa, who recorded a straight-sets victory over Denmark’s Clara Tauson 6-1, 6-2.

Poland’s Iga Świątek beat Viktorija Golubic of Switzerland 6-2, 3-6, 6-2, while Tunisian Ons Jabeur overcame Belarusian Aliaksandra Sasnovich 1-6, 7-5, 6-3.

In the last match of the day, American Ann Li went down to world number six Maria Sakkari from Greece 6-3, 6-3.