VVD, Gomez, Matip, Keita and Jota all potentially start that game, so that's 5 or 4 if you only include 2 centre backs. There's no point isolating a single game, the numerous amounts of injuries and the regularity of them contribute to the continual downfall. City lost there CB's and dropped almost 20 points last season despite them having an absolutely stacked squad.
Injuries, players out of form, poor tactical decisions, etc. It's not one thing, they all contribute. But injuries are defenitely a major factor and no where near a non factor like you're making out.
And seriously, Kabak and Davies were going to play? They had 1 session and they're going to start against the League leaders? LOL.