NEWCASTLE, England (AFP) - Mark Viduka's Achilles injury is more serious than had been thought and the Australian forward is facing a lay-off of up to six months, Newcastle manager Kevin Keegan revealed on Thursday.

Viduka, 32, is due to to have an injection this week that is supposed to help him recover from a niggling Achilles problem without him needing to undergo full-scale surgery.

Keegan had hoped that would enable the striker to be fully recovered in time for the start of pre-season training on July 7.

But he now admits it will be mid-August at best and November at worst before Viduka is ready to play again.

"We will know more in two weeks and we'll inform you then," Keegan said. "If it is three months it won't be a major blow.

"Mark has been very good for us and when he has started we have generally played well and got a result.

"But if it is six months that will be a major blow."