Ahly defender Saad Samir, who recently returned to action after recovering from injury, damaged his Achilles tendon during the 2-0 win over Zimbabwe's Platinum in the African Champions League late on Saturday.
"Medical scans have showed that Saad Samir suffers from a rupture in his Achilles tendon," Ahly's doctor Khaled Mahmoud told the club's official website on Sunday.
"The player will undergo surgery during the coming days and the operation will determine how long he will stay out of action."
The 30-year-old defender left the pitch of Ahly's game against Platinum in the 3rd round of the group B games only 15 minutes from the start after sustaining a serious injury.
Samir recently returned to the squad after recovering from a knee injury that sidelined him for more than three months.
"Samir's injury is more serious than Ajayi's, as he recently returned to action after recovering from another injury," Ahly coach Rene Weiler told the post game press conference.
The record eight-time winners Ahly, who are eyeing their first Champions League crown since 2013, moved level on six points with Al-Hilal and Tunisia's Etoile Sahel after three matches in what could be a tight race for the two quarter-final tickets.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)