Ashour missed Ahli's previous three games due to an ankle injury but was expected to feature in the Hodoud encounter.
But he picked up a hamstring complaint that could prevent him from making his comeback against the military club.
"Ashour missed today's training session after straining a hamstring muscle," Ahli doctor Magdi Abdul-Aziz told FilGoal.com on Sunday.
"He is undergoing treatment but we are not sure whether he can take part in Tuesday's match."
The 24-year-old's absence leaves a big void in Ahli's midfield, given his tireless defensive work which annoys opposing forwards.
Ahli will be also without mercurial midfielder Mohamed Barakat, who is nursing a knee injury, and Amir Sayoud after the Algerian playmaker sustained a groin injury.
The club, who are managed by Abdul-Aziz Abdul-Shafi 'Zizo' on a temporary basis, cannot afford to stumble against Hodoud if they are to cling to the coat-tails of arch-rivals and league leaders Zamalek.
Zamalek have 27 points from 12 matches, seven clear of fifth-placed Ahli who played a game less. The Cairo duo clash in an anticipated derby on December 30.
Ahli are seeking to win a seventh consecutive league title while Zamalek are eyeing their first triumph since 2004.