Well it's obvious that the absence of two players Kelvin Debruyne and Rodi has contributed to their poor performance and this should let Pep Guardiola to know that the team still needs strengthening,
Yes mate I think Manchester city are suffering from extreme injury problems and the match against arsenal exposed how even them can fall without the right players, they are missing Kevin and some players are playing the wrong roles or aren't playing in their natural position.
One of the biggest mistakes they made was to sell some very important players and they didn't improve their midfield
I guess you are talking about players like Gundogan which was replaced by Kovacic from Chelsea. Every strong team must have a weakness and that of Manchester City was noticed and that was used to take advantage of them. It shows that they can’t do without some certain players even if they substitute with others. Lack of De Brune in the squad have not been showing too much when they have been playing other teams but now that they face a big team like Arsenal, they have both miss out of the game with De Brune and Rodri. This is just a game and it happens to anyone it wishes at some point and I think Manchester City won’t be weakened by this not to do better in their next match in the league.