Davydenko is the fourth Russian casualty in Sydney

The world number three quit his second round match with Frenchman Paul-Henri Mathieu after losing the first set 6-4.

Davydenko, who joins female compatriots Svetlana Kuznetsova and Nadia Petrova on the sidelines, said he had a possible stress fracture in his foot.

"If that is the result I will pull out of the Australian Open," he said. "I will go to Melbourne and have a scan."

Another Russian, Dmitry Tursonov, also pulled out before his first match in Sydney after hurting his wrist in the warm-up.

I'm more experienced, I'm tougher mentally, my footwork is better Marcos Baghdatis

Marcos Baghdatis and defending champion James Blake both progressed smoothly however.

Baghdatis defeated Czech Jan Hernych 6-4 6-7 6-3, while Blake beat Australian wildcard Nathan Healey 6-2 6-4.

Baghdatis, a shock finalist in last year's Australian Open before losing to Roger Federer, said he was in the best shape of his life heading into next week's event.

"I'm more experienced, I'm tougher mentally, my footwork is better," he said.

"I've had five weeks preparation, I feel a lot faster and I feel better both physically and mentally."