Earlier this month Mancini walked into one of his press conferences wearing a Platt mask, a jovial reference to his recent habit of asking his number two to speak on his behalf.
And it was Platt again who addressed reporters as City previewed their midweek Barclays Premier League trip to Wigan.
The former England midfielder claimed it had nothing to do with the fact it was the Italian's birthday, but said there was work to do with the game coming just three days after the last.
Platt said: "It's not just his birthday, the games are coming thick and fast and his words are in the system."
Platt went on to speak positively about the champions' defence, with Sunday's goalless draw at Chelsea bringing a fifth clean sheet in seven Premier League games.
Among their key performers has been 19-year-old Nastasic, who is now blocking the return of fit-again England centre-back Joleon Lescott to the team.
The Serbian, signed from Fiorentina on deadline day in August, has started the last seven matches in all competitions.
Lescott missed part of that sequence with a back injury but has been back in contention for the last three games.
Platt said: "That is testament to him (Nastasic). He has stepped in. The first couple of games he has had to get used to English football but he has done that very quickly.
"The really, really good performance - he has had several good ones - but the real one where it might have been a bit alien to him was when we went down to West Ham.
"You knew the ball was coming in, they were hitting the diagonal balls towards Andy Carroll and I thought he acquitted himself exceptionally well.
"You get that a lot in the Premier League that you don't get in Serie A and it shows there is an old head on young shoulders to adapt to that."
Lescott did not even make the bench at Stamford Bridge with Kolo Toure preferred as back-up central defender, but Platt does not think much should read into that.
He said: "Joleon is fine. He will be available for selection like he was available for selection at the weekend.
"He has been available for selection for a few games, but we can only put 11 on the pitch."
City also have no worries about the fitness of key defender and captain Vincent Kompany.
There were suggestions the Belgian could be rested after defying the knee injury suffered in last week's Champions League clash against Real Madrid to play 90 minutes at Chelsea.
But the 26-year-old, who was outstanding at Stamford Bridge, has not suffered any reaction that would prevent him playing again.
Platt said: "It's not a case of it being too much at all. Vinnie would have still been feeling the effects of the injury that he picked up last Wednesday in the game but he got through the game and got through it very well.
"We don't really have any concerns for him tomorrow [Wednesday] night."
While City were solid at the weekend, they were also frustrated at their failure to convert any chances.
They have not reproduced the brilliance of the early part of their last campaign, when by this stage, 13 games, they had scored 43 goals, 11 more than their current tally.
Platt said: "You can't draw comparisons to last season. I don't know how many goals we are down from last season, but we were setting records left, right and centre last season so that was a false thing.
"We would like to have a few more of course because it would have got those extra victories, but 13 games gone, one point off the top, still unbeaten; there's enough in there to be pleased about."
Platt is taking little notice of the league table ahead of the clash at the DW Stadium.
Wigan have won just four games and remain in the lower reaches of the table, but Platt feels they have produced some eye-catching play.
"They are all tricky games," he said. "Wigan have a great deal of belief in themselves and have even when they haven't got results.
"Roberto Martinez puts that into his teams. He wants them to play, they make the field very big when in possession and because of that they can cause you problems."
Left-back Gael Clichy is again out with an ankle injury.