The Manchester City striker picked up a knock in training on Saturday but the Azzurri coach is confident that his No.9 will be fit to face Giovanni Trapattoni's men.
"We'll see how Mario is on the training pitch," he told reporters at a press conference on Sunday evening.
"But he is much better than he was yesterday. If he trains [on Sunday night], then he will be fit for tomorrow."
After back-to-back draws, against Spain and Croatia, Prandelli is expected to change his formation from 3-5-2 to 4-3-1-2 for the must-win meeting with the Irish.
Some have interpreted that as an act of desperation, but the former Fiorentina boss insists that this is not a panic move.
"I don’t make choices just for no reason when I wake up in the morning," he exclaimed. "When you choose certain players, you have to take into account the system.
"We must always be elastic, balanced and reasoned. That means picking the players who suit that system. Every time I make a choice, it is carefully pondered.
"We do not just wake up and then decide to change three defenders. We have been working on this every day for a month!"
Ireland were easily beaten by both Spain and Croatia, but Prandelli is not taking victory in Poznan for granted.
"Spain were only 1-0 up after 70 minutes," he pointed out. "This is a very organised side, they play football and like to fight. The danger comes from the long balls forward, the flick-ons and the counterattacks.
"In all honesty, I am surprised Ireland are already out, but they were very unlucky against Croatia. We can see they prepared with a certain plan, but by conceding so early they were no longer able to adjust to the new situation.
"But I'm convinced we have the means at our disposal to go and win the game."