Melbourne  - The Australian Open has lost injured world number five Nikolay Davydenko as the Russian withdrew due to a nagging heel injury.

The opening Grand Slam of the season suffered its first high- profile defection through the pullout. Also on the possible danger list are Maria Sharapova and world number two Serena Williams.

Neither have played for months - Sharapova has missed six months - but both insist they will be ready for the major, which begins in 11 days.

Davydenko pulled out of this week's ATP event in Chennai, India, after losing in the second round, saying he needs time for his foot to properly heal.

"I'm pulling out because my left heel has been very painful over the last few days," he said. "I need to see doctors before I know when I can return." (dpa)