The 29-year-old has lived his international career in the shadow of Castrogiovanni, who broke a rib against England two weeks ago, but is now relishing the chance to take a leading role for his country.
Cittadini, who has ten caps to his name, will pack down at tighthead opposite Ireland's Cian Healy and is only to aware a lot rests on his shoulders if Italy are to break their duck in this year's Championship and chalk up a first win in 13 over Saturday's opponents.
On the other side of the scrum Michele Rizzo will be making his RBS 6 Nations debut. With just two caps to his name he will be looking to Cittadini to set the example and he will be buoyed by the Treviso player's optimism.
"I feel ready. Actually to be sincere, I have never felt so ready," said Cittadini.
"To return to the national side after a serious injury in 2008, when I fractured my tibia and fibula, is a great line to have crossed.
"The muscle tone of my right leg has never returned to its former level and I have to do a lot of physiotherapy in the gym and elsewhere but the passion I have inside helps me.
"Ireland? We know that it won't be easy in Dublin but we have studied our opponents well and we go there to get a result.
"It will be an important test to check where our growth is.
"We need to do well in the scrum. [Our coach] Jacques [Brunel] wants 100 per cent from us so we have a stable platform. We won't let him down."