Al-Sayed fell in pain all of a sudden with no challengers in close proximity when he slipped while running towards a loose ball.
The veteran goalie received quick treatment and wasn't taken off, although he kept limping till the end of the game.
"Initial diagnosis indicated that he has a knee ligament sprain. We will determine the full extent of the injury after checking his X-ray image," Al-Monayeri said after the game.
Al-Sayed is due to undergo further medical examinations at Zamalek on Wednesday.
Moreover, Zamalek defender Amr Al-Safti sustained a knock to his ribs, and thus was substituted in the first half.
"Al-Safti will take no part in Wednesday's morning training session and will undergo medical tests later on the same day," added Al-Monayeri.