The Italy international, who has played only twice this season, first suffered a thigh injury and then a microfracture to his foot.
Italy right back Abate limped off in Glasgow as Milan hammered Celtic 3-0 in the Champions League on Tuesday, while Abbiati is suffering from flu.
Their absence adds to a lengthy injury list that includes defenders Phillipe Mexes, Christian Zapata, Cristian Zaccardo and Mattia De Sciglio, midfielder Sulley Muntari and attackers Robinho and Giampaolo Pazzini.
Milan are 13th in Serie A after a poor start to the season, and take on Catania with amid a backdrop of boardroom unrest.
- Sports & Recreation
- Christian Abbiati
- Ignazio Abate
- Massimiliano Allegri