The 25-year-old has not played since the New Year's Day win over Southampton, and refused to take a fitness test before the game at Arsenal three days later.
A scan last week failed to determine the source of Anelka's back and groin pain, so Kevin Keegan is hoping a further test will give more conclusive results. KK was not happy with Anelka's late withdrawal from the squad to face Arsenal, but has no doubt the mystery injury is genuine.
"Nicolas is getting pains in his back and groin," he told Sportinglife.com. "He has been for one scan, which showed nothing - but if he has a problem anywhere the next one will pick it up because it is much more thorough.
"I have no doubt there is something wrong with him - we just don't know what it is."
City have been forced to do without Anelka against Arsenal and Palace in the Premiership, although it must be noted that they have managed pretty well, especially with the ever-improving Robbie Fowler leading the City frontline.