The defending Premier League champions fell 15 points behind leaders Manchester United over the weekend after suffering a 2-0 defeat against Everton.
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"There is an appreciation of Roberto from the supporters and the owners," Platt told reporters.
"The expectancy levels of Roberto Mancini are a lot higher than what people think. If people want to talk about rumours and negatives that is up to them. We can't stop that.
"If people want to do things like that, they can. All I know is that during his career he has won things. That is what his focus, desire and intensity is about.
"He won't want stop wanting to win things. He will regroup from this and by the time we play Newcastle he will have 100 per cent focus."
Mancini has won two major trophies - the Premier League title and the FA Cup - since succeeding Mark Hughes at City in 2009.