Platt expects all thoughts of Wembley to be put aside as both clubs concentrate on outstanding issues in the Barclays Premier League.
City, although out of contention for the title, still need the points to secure second place while Wigan have a more urgent requirement at the opposite end of the table.
Roberto Martinez's men are in the bottom three but could climb out of the relegation zone if they can pull off an unexpected victory at the Etihad Stadium.
Platt said: "It is not a case of because we are playing them tonight [Wednesday] we will know how to play them in the cup final. I don't think it has any correlation whatsoever.
"Each team has four or five games before then.
"Roberto Martinez is a good manager and I am sure they are looking at the next four or five games and thinking, 'If we can get away from that relegation threat then we can enjoy the day'.
"It doesn't take the shine off the day but retaining Premier League status for them is paramount.
"I am sure if they have it in the bag by then they will be delighted and they can go and enjoy a Wembley cup final."
As well as reaching the cup final, Latics have also found form in the Premier League, claiming 10 points from their past five games.
Wigan have made a habit of staging successful escape acts in recent seasons and they could be in the process of doing so again.
Platt said: "I think you see it not just with Wigan. It is very dangerous to try and predict the three teams who will get relegated in February.
"The last six weeks of the season, form seems to go out of the window.
"Inevitably, if you are down there and have done it year on year as Roberto seems to have done then you have that experience to take teams through."
City are unlikely to risk playmaker David Silva as he continues his recovery from a hamstring injury.
If manager Roberto Mancini wants to make changes after the energy-sapping weekend display at Wembley, he could consider Micah Richards, Maicon or Jack Rodwell, who are all training again after lay-offs.
Meanwhile, City striker Sergio Aguero said he has apologied to Chelsea's David Luiz following his two-footed challenge on the Brazilian in Sunday's FA Cup semi-final at Wembley.
Both of Aguero's boots made contact with the upper part of Luiz's left leg as the two tangled late in City's 2-1 win, which secured a place against Wigan in next month's final.
Luiz himself responded positively to the tweet himself on Twitter, drawing a line under the incident.
The Argentina international will face no action over the challenge after the Football Association confirmed referee Chris Foy had seen at least part of the incident and acted on it during the match, meaning the governing body were unable to deal with it retrospectively.