MELBOURNE (AFP) - Third seed Maria Sharapova and former world No.1 Caroline Wozniacki survived frights at the Australian Open on Thursday but dug deep to grind their way into the third round.
Russian star Sharapova, the 2008 champion, came through a brutal three-set marathon against 44th-ranked Karin Knapp in intense heat.
She battled temperatures of up to 42 deg C and a third set lasting nearly two hours to down the Italian 6-3, 4-6, 10-8 and set up a clash with France's Alize Cornet, who broke down in tears of frustration during her game.
"I worked really hard in the last few months and I wanted this match," said Sharapova, after making extensive use of ice vests and ice packs to keep cool in the sizzling conditions.
"I didn't play my best tennis; I didn't do many things well. But I got through it, and sometimes that's what's important."
It was not easy for the 26-year-old, who is coming back from surgery and is desperate to win a fifth Grand Slam, with her last coming at the French Open in 2012.
Her serve let her down and she only converted seven of 20 break points against a gritty opponent who refused to give up.
She said it was now important to give her body plenty of recovery time before facing Cornet on Saturday.
"I'll take it easy tomorrow. That's the beauty of a Grand Slam, you have that day in between," she said.
Wozniacki, who this week said she had never been happier after getting engaged to golf star Rory McIlroy, also had a wobble against unseeded American Christina McHale.
The Dane, seeded 10th, blasted through the first set 6-0 but her form then deserted her. She won just one game in the second before regrouping to take the third 6-3.
She benefited from playing with the roof shut on centre court after the tournament's extreme heat policy was enforced during the third set of Sharapova's match.
"I was really, really pleased and happy about that," she said, expressing sympathy for Sharapova and Knapp having to brave the oven-like conditions.
"I was lucky to play on Rod Laver Arena. First of all, it's a great stadium and second, I think playing out there in that heat must have been tough and very brutal."
Despite the wobbles, Wozniacki, who ended 2010 and 2011 as world No.1 but has never won a Grand Slam, said she believed she could finally make the breakthrough at Melbourne.
"I think you always believe you can win, but I still have quite a few matches to go. So I'm just thinking one match at a time," she said.
Other players safely through included fifth seed Agnieszka Radwanska, a quarter-finalist here in all of the last three years. The Pole beat Olga Govortsova of Belarus 6-0, 7-5 and now plays Russian Anastasia Pavlyuchenkova.
Spain's 16th seed Carla Suarez Navarro, Romanian 11th seed Simona Halep and 20th seed Dominika Cibulkova also progressed on a day which was interupted for some four hours on the outside courts when play was halted owing to the heat.
Defending champion Victoria Azarenka plays in an evening match against Czech Barbora Zahlavova Strycova with world No.1 Serena Williams in action on Friday.