Murray had been leading Andrei Pavel 6-2 3-1 when the Romanian quit after 45 minutes with a back injury that kept him out of the sport for most of last year.

"I guess if you want to do well in the tournament, it's good to conserve some energy... hopefully that was a good thing," fourth seed Murray said, weighing the pros and cons of a quick outing.

Serena Williams did not waste too much time either, cantering through with a 6-3 6-2 win over China's Yuan Meng. The American second seed is seeking a fourth Australian title after winning here in 2003, 2005 and 2007.

"It was a little hot for me today," she smiled, sipping a drink. "It was a case of taking my time, not giving 1,000 percent, you know?

"I was getting super thirsty out there - at one stage I had to stop and have a drink of water," she laughed.

"It was definitely extreme conditions," she added, stifling a sniffle. "I do have a little bit of a head cold... I hope that goes away."

SCORCHING HEAT

World number four Elena Dementieva survived the scorching heat to see off Kristina Barrois. Unbeaten so far this year after picking up titles in Auckland and Sydney, Dementieva beat the German 7-6 2-6 6-1.

"It was a very tough match, especially because of the weather conditions today. And also it was not easy for me to come here after playing so many matches in a row," the blonde Russian said.

"I'm sure I wouldn't have minded one or two extra days before. But those are kind of days you have to survive. I'm just very glad I was able to do it."

She will next meet the winner of the match between Russia's Vera Dushevina and Iveta Benesova of the Czech Republic.

Polish ninth seed Agnieszka Radwanska was an early casualty, however, falling 7-6 4-6 6-1 to Ukraine's Kateryna Bondarenko.

Australian former world number one Lleyton Hewitt was due to do battle with 13th seed Fernando Gonzalez later on Tuesday and Serena's sister Venus was to play Angelique Kerber.