The foward has been confirmed as an absentee for the weekend clash at San Siro after picking up an injury on Tuesday
The Uruguay international had been in doubt for the clash after suffering a sprained ankle in his side's 2-0 Champions League victory against Villarreal on Tuesday.
It has been suggested that Cavani could take up to two weeks to fully recover from problem, which would rule him out of Uruguay's upcoming 2014 World Cup qualifiers against Bolivia and Paraguay.
Napoli have not yet commented on the extent of the 24-year-old's injury, which comes as a huge blow to the fourth-placed Serie A side.
Goran Pandev, who is on loan from Inter, is expected to deputise for Cavani against his parent club.