Richards has not played since injuring knee ligaments last October, but is available along with midfielder Jack Rodwell who has not featured since the start of March.
"Micah's been back in full training for almost two weeks and he's played a couple of EDS (Elite Development Squad) games so he's available for selection," Platt said.
"Whether he could get through a full 90 minutes is another story.
"Jack could also make the squad though, like Micah, I doubt he would be ready for a full game. Squad selection and team selection are two different things and you can't afford to have too many players starting who you suspect you may have to substitute at some point."
Playmaker David Silva is unlikely to rushed back for Wednesday's clash, as City, who are second in the Premier League but 15 points behind leaders Manchester United, refuse to take risks with his fitness.
Silva missed Sunday's FA Cup semi-final win over Chelsea after picking up a hamstring injury in the Manchester derby on April 8.
"The game on Sunday came a bit too early for David, though if we'd have pushed it, he probably could have played some part and had it been the last game of the season, we may well have done, but we felt the risk was too great," Platt said.
"I think playing him in the game with Wigan could also be a risk so we'll probably be pragmatic and give him a bit more time."
Wednesday's match is a dress rehearsal for the FA Cup final after Wigan won their semi-final against Millwall on Saturday.
Relegation-threatened Wigan are 18th in the Premier League and three points off safety but with two games in hand on their closest rivals.