Asked whether there was any chance of Mancini quitting the club that has just handed him a new five-year contract, Platt insisted: "No."
He added: "It's (the pressure) NOT getting to him. I know Roberto, I know his desire to win - and what he is here to do is to win.
"He signed a five-year contract in the summer, which was given to him by virtue of the fact that he's the manager of the champions.
"The last time I looked, we were two points off the top in third place after 10 games - with 28 to go. That's 84 points to play for - and we're two points behind the leaders.
"It's hardly a crisis."