Yet she again made an early exit, losing 7-6 (7/2) 6-3 to Romanian Sorana Cirstea. The defeat follows hot on the heels of a second-round exit in Brisbane and a first-round defeat in Sydney.

Stosur said: "I am extremely disappointed. It's certainly not what I wanted, not just this tournament but the whole (Australian) summer.

"I think it was one of those matches where I wasn't taking charge and she was playing super aggressive.

"She would either hit great balls or could miss by a long way.

"She hung in there and kept going for it and eventually got better and better. She played a very, very good match and you have to give credit where it's due."

As for the pressure on her shoulders coming into the event, she added: "There's probably nothing greater than my own expectation.

"I really, really wanted to do well here and over the summer and I did everything I could to try to give myself a good opportunity. But it obviously didn't happen.

"I know everyone was behind me and it's disappointing that I won't get another chance to step out on court."

Stosur's struggles were in stark contrast to the form shown earlier in the day by Petra Kvitova and Maria Sharapova, who both posted comfortable victories.

Kvitova, the Wimbledon champion and second seed in Melbourne, cruised past Russian Vera Dushevina 6-2 6-0 on Rod Laver Arena while fourth seed Sharapova demolished Gisela Dulko 6-0 6-1.

Dushevina made a strong start, holding serve and breaking Kvitova on her first opportunity to establish an early lead. But once the Czech clicked into gear it turned into a one-sided contest as Kvitova rattled through the remaining games to move into round two, where a meeting with Spaniard Carla Suarez Navarro awaits her.

"After a slow start it was fine," said 21-year-old Kvitova. "But I can improve my serve for sure.

"The score looks easy but it wasn't, the games were very close and I am glad I am through."

Fourteenth seed Sabine Lisicki, a Wimbledon semi-finalist last year, survived a scare to advance courtesy of a 6-2 4-6 6-4 defeat of Swiss qualifier Stefanie Voegele.

Lisicki had the trainer on court, seemingly taking her pulse and blood pressure as she looked to be wilting in the 35 degree heat, but she still found the reserves to hit back from 4-2 down in the final set to come through.

Maria Kirilenko, seeded 27, ousted Jarmila Gajdosova while there were also wins on day two for seventh seed Vera Zvonareva, ninth seed Marion Bartoli, 15th seed Anastasia Pavlyuchenkova, 17th seed Dominika Cibulkova and home favourite Jelena Dokic.