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Tomljanovic, who is working her way back slowly from an injury-ravaged 18-month lay-off, started brightly enough against No.30 seed Dayana Yastremska, but eventually lost 3-6 6-3 6-3.

Aleksandar Vukic was next, losing 6-4 4-6 6-3 7-5 to China's Zhizhen Zhang, and Jordan Thompson, who has an ATP title to his name, soon followed after a calamitous collapse.

Like Tomljanovic, Thompson won the first set of his match against Maximilian Martere, but the German thrashed the Aussie thereafter to claim a 3-6 2-6 0-6 victory.

Chris O'Connell didn't even make it to the court for his match against Austrian qualifier Filip Misolic, withdrawing before it had started because of injury.

Before the start of the day, there were 11 Australians in the singles draws, but the chances of any making it to the second week, of even the end of the first, now appear to be slim at best.