Australia's Lleyton Hewitt [Images] kept his cool on a blistering hot summer's day to reach the semi-finals of the Sydney International at Sydney on Thursday while his main rivals all melted.

The world number three breezed into the last four of the Australian Open warm-up event with a 6-1, 7-6 win over Swede Thomas Johansson to be the last remaining seed in the men's draw.

Fourth seed Romanian Andrei Pavel, Spanish fifth seed Feliciano Lopez and Taylor Dent, the big-serving American seeded eighth, all succumbed to lower ranked opponents as the temperature at Sydney's Olympic tennis centre soared to 42 degrees Celsius.

Pavel fell to little-known Czech qualifier Ivo Minar 2-6, 7-6, 6-4, while Lopez succumbed to Radek Stepanek 6-3, 6-2.

Dent, who beat Hewitt in last week's Australian hardcourt championships, failed to finish his quarter-final with Max Mirnyi of Belarus, quitting halfway through the first set after feeling ill.

"I was feeling a little bit light-headed, dizzy and my energy was going pretty fast," Dent said.

"I saw the doctor and told him what was happening. He said just try and stay out there... but it was getting worse minute by minute."

The carnage was not just restricted to the men's singles. India's Leander Paes [Images] twisted his foot during a doubles match and is in doubt for the Australian Open while Czech Tomas Berdych also quit the doubles after suffering a stomach problem.

In the women's draw, Russia's [Images] world number 13 Nadia Petrova quit her match against Chinese amateur Peng Shuai because of heatstroke. The fifth seed was trailing 6-3, 4-2 at the time.

Of the five Russian women who entered the event, only third seed Elena Dementieva remains in the draw. The French and US Open finalist beat Swiss Patty Schnyder 6-4, 1-6, 6-1 to set up a possible semi-final with world number one Lindsay Davenport [Images].

Peng will play Alicia Molik [Images] in the other semi-final after the rapidly-improving Australian beat Colombia's Fabiola Zuluaga 6-1, 6-2.

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