While Ben Mohammed is out injured, his compatriot Chaalali would miss the crucial clash against tournament debutants having received two yellow cards in the earlier games against Angola and Mali.
According to a statement by the Tunisia Football Federation, Ben Mohammed, who has a muscle pain will need at least a four-day rest while Chaalali will be available for selection again if the Eagles soar into the knockout stage.
Tunisia are making their 19th Afcon appearance in Egypt, having featured in each of the last 14 editions, while last missing out in 1992.
They are tied on two points with Angola in Group E and need a win to stay in the hunt for another Afcon title.
The Carthage Eagles won their only Afcon title in 2004, defeating Morocco 2-1 in the final in their home tournament.