Dinara Safina has retired at 5-4 and set point down against Maria Kirilenko in the ofurth round of the Australian Open after experiencing a recurrence of the back injury that plagued her last fall.

"My back again. It suddenly hit me. It was getting worse and worse," said Safina. "It's really, really terrible."

Safina had missed the first tournament the yer in Brisbne to continue her recovery from the injury, but was pain-free during the Australian Open until Sunday. "The only thing I felt a little bit stiff in practice like during the serve, but nothing serious," she said. "Today I warm up, it was fine. I was cooling down, and I start to feel a little more pain.

"Suddenly I played a long game at 3-2. I won the game. I turned to my coach. I said, 'I cannot move anymore.'"

The world No. 2 was not sure how long it will be before she can play again. "I have to go back to Germany to my doctor to speak with him. I mean, I did MRI before I came here, and my bone edema was getting much smaller.

"I just don't know what happened. It's shocking.

"Exactly the same like in Doha [last fall]... I mean, the physio asked me to lie on the table. I said, I cannot lie. I cannot make any movement. Whatever I try to move, it hurts terribly."