كتب : Sherif Tarek
"I felt pain in my hamstring during training and left the pitch as a result," he told FilGoal.com.
"I should undergo medical tests on Monday to determine the full extent of the injury.
"My chance to feature against Ismaili will be slim if the injury prevents me from training the next couple of days."
Egypt international Fathallah stressed that he's eager to participate in anticipated match, which takes place in Cairo.
"I really want to play in that match, even if I'm injured," he said. "I will do my best to be fit on time."
Fathallah, whose contract with the Whites runs out in the summer, was expected to extend his stay at the Cairo side these days.
However, the sacking of wealthy businessman Mamdouh Abbas as Zamalek's president put his new deal on hold.
Fathallah, who's renowned for his aerial prowess, has scored four league goals so far this season.