Pantilimon is set to remain between the posts for the final.
Platt said: "Your goalkeeper that backs up the number one has a thankless task. He is always away in the hotels, he sits on the bench - when does he ever get on? When does he ever get a game?
"It is important he plays big games so that he is ready for that.
"That is what Robbie (Roberto Mancini) has done over the years. He has allocated domestic cup competitions to that goalkeeper.
"I think it would have been unfair to Costel to change the goalkeeper.
"If he keeps his place the final will be a different game, a different choice, but I don't think he has done anything wrong to warrant not playing in that final."