City have to travel to Barcelona for a game on the Wednesday. If players are going to play in both games, it would obviously be better for them to play on Saturday rather than at Sunday teatime.
However, City have a big enough squad to play a different eleven in each game. City reserves should be good enough to outclass Wigan, as they did earlier this season. But in the FA Cup, you never know.
On the other hand, City may decide to write off the Barcelona game and concentrate on the treble. City will want to avoid humiliation in Barcelona but, even so, Wigan could then face a stronger team.