Italy host Georgia in Udine in their second preliminary match on Wednesday, but coach Marcelo Lippi has revealed no-one would be added to the squad in place of Grosso, who has fractured ribs, and Gamberini, who dislocated a shoulder.
Azzurri team doctors said Grosso would be out for about a month, and Gamberini would not be back for at least two weeks.
"There is no point in replacing someone who is going to sit in the stands," said Lippi, explaining why he had not called up replacements.
Italy, the reigning world champions, needed a last-minute goal to eke out a 2-1 victory over Cyprus on Saturday.
Antonio Di Natale, with his second goal of the night, secured an undeserved three points in this Group 8 game.