Gundogan has moved to Barcelona, while Bernardo and De Bruyne have been injured. Manchester City's performance hasn't changed much without these three, but naturally it has an impact on the quality of their game. Manchester City is still a team capable of dominating their opponents in a match, so it's not a big case that needs to be resolved as soon as possible.
Did you watch the Manchester City vs Newcastle match just now? If so, you know if they have lost their best form or if they played badly without Silva, Gundogan and De Bruyne. I don't see anything negative, that's because the substitute also had a good performance in that game.
I think the genius of Pep Guardiola has proven to be quite good at rotating their players when one of the important players is absent but substitutes are able to cover the gap. Yes, Pep Guardiola proved that when he faced Newcastle United, where they were able to dominate the match and were able to get 3 points in this match.
The stability of the Manchester City team is none other than because they have substitute players who are not much different from their quality with their core players. Leaving Mahrez, Gundogan and also the injury to Kevin De bruyne did not have a negative impact on Manchester city game in this match. They are really still going strong and it will be difficult for any other team to beat manchester city.