This is football so it's possible. I already set out the things that could happen to City before they even faced Man United for the FA Cup Finals. The competition is tight for the Premier League title so every City's player have to compete every week on a very high level. That may cause a lot of injuries to them and that's going to be advantageous to United who only have to maintain top 7.
One thing you most know about Man City team is that as long as premier league is consign no amount of injury that will going to affect Man City players, because if you check well in the premier league you can see that Man City second Eleven can win Arsenal, Liverpool or Manchester united, because they have it takes to be the England premier league best club. No list player in Man City all must everybody are in form.
Injury affects all clubs and that is no exception to any club no matter how strong and vigorous they are in the field of play. Saying injury can’t affect Manchester City players is false, when De Bruyne was injured, we can see the plenty problems that Manchester City was facing in the midfield until his return back in the pitch. The second eleven of Manchester City can’t win Arsenal and Liverpool, it is was that easy, the first team would have found it easier playing with these teams, so I don’t believe that is even possible to think of. Manchester City are good but you can’t give them that type of hype. The FA Cup final is going to be on an average level even though Manchester City has the better chance of winning the FA Cup final. Manchester United will try to win their first trophy of the season but looks very much impossible from this angle, but they can try their best.