Therefore, it is clear that Bruyne has suffered a serious injury, because it requires a very long recovery. Moreover, based on existing records, at least Haaland get injured too. But yes, fortunately Haaland did not suffer a serious injury so Haaland was still able to play. So ya, with these factors, I think it is natural that Manchester City is experiencing a decline in performance, because many key players are injured. Therefore, perhaps Manchester City no longer has a big chance of getting to the Champions League final this season.
Most of their injured players will soon be back because Kevin De Bruyne has almost fully recovered, and he is one of the key players in Manchester City's squad; therefore, if he recovers fully, the Manchester City squad will have some strength and will be a better team. Although only he can make the team better, there are other players in the team who are playing very well and will do well before Haaland recovers from injury. Nevertheless, even if all of them are back from injury, their chance of going to the Champions League final this season is not guaranteed because they don't have as strong a squad as they used to have in previous seasons, unless they sign more players in January, which might affect the team financially through Financial Fair Play.