Victory for Italy could see them progress to the knock-out stages of the World Cup for the first time at the expense of Ireland, and Castrogiovanni has revealed that his side are "not afraid" of their opponents.
"We are not afraid of anything. We want to make it a long, long day for them," Castrogiovanni told BBC Sport.
"We need to have the perfect game, physicality, good defence, no mistakes, a good kicking game, then we will have a chance.
"We will have to put pressure on them in every position. It will be a war in the forwards and the backs. We have a really good backline as well. It's always a war, it's rugby."
Castrogiovanni, 29, currently plays his club rugby for Aviva Premiership side Leicester Tigers.