Fourth seed Maria Sharapova [Images] overcame brutal heat and humidity on Sunday to beat Slovakian Daniela Hantuchova [Images] 6-4, 6-4 and reach the quarter-finals of the Australian Open.

The Russian finished off an impressive victory in 97 minutes to stop the 17th seed, who had toppled defending champion Serena Williams [Images] in the previous round.

"Today was probably one of the hottest days I've ever experienced in my life," Sharapova told reporters. "It was pretty brutal out there."

Sharapova will play compatriot and sixth seed Nadia Petrova in the quarter-finals.

The match was played with the roof closed over the Rod Laver Arena after officials invoked the tournament's extreme heat rule on the third straight day of scorching weather.

Temperatures reached 43 degrees Celsius, well above the 35 degrees at which the rule can be used.

On Saturday, Dutch teenager Michaella Krajicek suffered heat stroke and pulled out after playing one set against third seed Amelie Mauresmo with the roof open.

The timing of the Australian Open is a perennial issue.

Many leading players want it moved to March so they can have a longer lay-off to overcome injuries and prepare for the new season. The worst heat of the Australian summer is also over by March.

"I think for tennis players it would make our lives a lot easier," Sharapova said.

IMPRESSIVE DISPLAY

Sharapova produced another impressive display in fighting off Hantuchova, who broke her serve in the second game of both sets.

Hantuchova, vying to reach the last eight for the first time since 2003, broke Sharapova's serve in the second game of both sets and led 3-0 in the second.

But Sharapova was too strong and quickly got back on level terms before grabbing the crucial advantage in the eighth game of the second set, punching a forehand winner at the end of a long rally to break Hantuchova for the last time.

"I was a little bit sluggish in the beginning ... my rhythm was a little bit off. But I really kept my composure," the 2004 Wimbledon champion said.

Sharapova made the Australian Open semi-finals last year and beat Petrova in the quarter-finals at Wimbledon and the U.S. Open.

"She hits a very flat ball, a big server," said Sharapova.

Hantuchova needed a medical time-out for treatment on her left thigh after Sharapova broke her serve in the fifth game of the second set. She said she had pulled a muscle a couple of games earlier.

"Because of the thing I did with my leg, my movement was not as good as it was in the first set," said Hantuchova, who had hailed her win over Williams as a turning point in her career.

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