Zeljko Kalac has been included in Milan's squad for the trip to Arsenal, but is still doubtful for Wednesday's UEFA Champions League game.
The Australian goalkeeper dislocated a finger in training on Sunday to hand the holders a potential crisis for the game at Emirates Stadium.
Dida has already been ruled out of the first leg of the last-16 tie with a back problem and Kalac's injury will be assessed on Tuesday.
He has travelled with the squad to London, but remains a major injury concern for Milan coach Carlo Ancelotti.
If Kalac is ruled out, then Valerio Fiori, who has made just one appearance in eight seasons, will start with youngster Daniel Offredi on the bench.
But while Ancelotti sweats over the fitness of his goalkeeper, he has been boosted by the return of Alexandre Pato.
The Brazilian forward has missed the last three games with a knee injury, but is part of Milan's plans for Wednesday's game.