After the operation Gigi is expected to be out for 40 days and be back on time for the match against Roma on January 24th. In the meantime he'll surely miss the serie A matches against Bari (A), Catania (H), Parma (A), Milan (H), Chievo (A) and the Coppa Italia match against Napoli (maybe even the 1/4 finals in Coppa, if we eliminate Napoli, which are played between January 20th and January 27th).
P.S: If we eliminate Napoli then our 1/4 finals opponents in the Coppa will be Inter. The match will be played in Turin.