Cahill has been Crystal Palace's player of the season this term and one of the best signings in the Premier League, having arrived on a free transfer after leaving Chelsea last summer.
However, the 34-year-old is likely to play no further part this season after pulling up with a hamstring injury against his former side on Tuesday night.
Palace have built their season around his form and leadership at the back, with their defensive record making up for a poor return in front of goal.
However, without his influence, Sakho - likely to start in Cahill's place at Aston Villa on Sunday - must find his feet quickly.
The Frenchman, who had been a key figure himself before this season, has made just eight League starts so far in 2019-20 after struggling to find form between various injury problems.
Predicted Crystal Palace XI (4-3-3): Guaita; Ward, Dann, Sakho, Van Aanholt; Milivojevic, McArthur, Kouyate; Ayew, Zaha, Benteke