Viduka struggling to make pre-season with Newcastle
The 32-year-old who formed the three-pronged frontline with Martins and Michael Owen which did so much to ease the club away from the relegation zone at the end of last season, missed the last game with an Achilles injury.
He had been battling the problem for some time and had an injection which it was hoped would cure it.
However, boss Kevin Keegan admitted if it did not, surgery could be required, and that would sideline the player for between three and six months.
Viduka is due to see his specialist once again early next month, and although the club are hopeful he could be ready for the start of the campaign, he could miss most of pre-season.