Manchester City will once again dominate the Premier League if de Byrune returns to the squad.
But Kevin De Bruyne is out until early next year, thus if your logic is right, City will struggle until early next year, hell, if that happens they'll be out of the title race by then. Pep and City can cope without any player, but it's not possible to deny the fact that some players make them play a whole lot better, like KDB.
City have also missed Rodri greatly for the last three games, they lost all of them without him, he is back for the next game against Brighton, and that should give City a lift. Pep is a genius, thus i trust him to find a solution to their current problems. If the rest of the league is celebrating City's dip in form, they should know better because City come alive when it matters the most and they can go on long winning runs, they remain favorites to win the title for the fourth time in a row.
Without Kevin De Bruyne, it is very difficult to keep the performance stable. But it is not impossible. Last season we saw consistent good performances from City. The team has consistently played well in the Champions League and Premier League and won the title. However, the City midfielder will not be with the best player squad this season. City's performance is likely to be erratic. But coach Guardiola is experienced. He may now employ a different match strategy to stabilize City's performance. But it will be very difficult for City. Kevin De Bruyne has been with City for a long time. Kevin De Bruyne has been with City since 2014 if I'm not mistaken. So it will be very difficult to fill the void of Kevin De Bruyne.