Manchester City will be defeated when they play Newcastle.
There is a huge chance that this could be possible, but we are talking about the treble winners here, and the newly crowned UEFA super cup champions, definitely you cannot rule them out even before the game has started. If City were playing away in this game, i might have agreed with you, in the St James' Park, with all the injuries, it'd be a mountain that City might just fail to climb.
Having said that, the game is at the Etihad, and more often than not City find their rhythm when they play at home and with their crowd cheering, don't get me wrong, i don't mean City must win because they are playing at home, at least not with all the injuries they have to worry about, but playing at home will help them so much to maybe get over the line. It is going to be so intense and interesting, we don't say this too often, but City might actually be happy if they get a draw, considering the state they are in right now.
If placing the prediction of Man City defeat against Newcastle tomorrow due to the injury of several key players, in my opinion that is not quite right. The mentality possessed by Pep Guardiola squad is inversely proportional to that of Newcastle, we can see the number of EPL trophies in City cupboard as proof.
Along with this, Newcastle comeback has not been tested in my opinion, the opening match they won against Aston Villa cannot be a complete benchmark. It makes sense to say that this fight will end in a draw, because that's more likely.