كتب : Hatem Maher
Fathi, one of Ahli's indispensable players, has been struggling with a groin injury he picked up last month.
He missed the team's 3-0 Champions League victory over Libyan side Ittihad and was doubtful for the Egyptian Cup round of 16 clash against arch rivals Zamalek.
But the Egyptian international handed Ahli coach Hossam Al-Badri a major boost by fully recovering from his injury ahead of the anticipated tie.
Striker Mohamed Fadl has been also declared fit after shrugging off a minor hamstring complaint.
Al-Badri would have been left in a selection dilemma had Fadl failed to make Ahli's squad for the derby after Emad Meteb, the team's top scorer in the league with nine goals, was ruled out with a back injury.
The Egypt striker is the only big-name absentee from Ahli's squad.
The Red Devils are seeking to complete the double after wrapping up a sixth consecutive Egyptian Premier League title.
They drew 0-0 and 3-3 with Zamalek in their two league games this season.