Manchester city cannot be tagged as crumbling yet, they have lost only two game this season and the losses were just immediately after they began to suffer some Injuries, something that is common amongst all team, whether big or small there are times injuries could affect any team so bad it will reflect in their performance aswell and i think it's same thing Manchester city is suffering at the moment.
No matter the small challenges Manchester City are having this period due to the injuries some of there players are having doesn't make them a weak team irrespective of there last match they lost against Arsenal, if you watch the match you will see they played very well there performance was very impressive.
And besides how can we say is not doing well when they are standing on the third place on the table, so what they are just facing is a normal challenges that happens all the time but that shouldn't be a serious challenge for them not to go far on this season because they have many games ahead of them and they are in a good chances of wining almost all the awaiting matches and before two or three of there next matches Kevin de Bruyne maybe back from his injury and before you no Manchester city is on the first position on the table because one of things about them is that no matter there poor performance but when they peak form, they become unbeatable.