Beside some main player injured, there are several things that make Manchester City performing badly this season, because Pep strategy already known to many club. Game style The City can be read and can be overcome by other coach. It's the same as Jose Mourinho today, his strategy outdated, other coaches can easily tackle it, and won it when face to face. I think, Pep must accept the reality if his period is over, he must learn something new immediately and learn to use new strategies for The City. I am sure even Rodri has returned to the squad, Manchester City will still be easy to defeat because others club already know what pep guardiola does.
Besides the injured of some key players and monotonous of the strategy/tactic applied by Guardiola, I assume Man City players have also a problem with their mentality. They are getting more often to get a lose, they have no longer the mentality of the champion that always struggle to win each match. Now, they may feel not really confident to face any team in EPL. It is actually the responsibility of the coach that can improve the mentality of the whole players. Since this problem continues, I think the players may begin to doubt the capability of Guardiola to handle Man City squad. The crisis of confidence of the whole players brings very bad impacts for the performance. This is actually a fundamental problem that Guardiola must be solved as quick as possible. Sure, even Rodri has recovered, it won't influence much if the problem of mentality is never solved.
I wouldn't go so far as to say they might not be confident against any team, that's not true. I also don't think they lack a championship mentality now because one bad season doesn't mean anything yet, after all it's impossible to win every season inside the EPL for years. It's still not Bayern inside the Bundesliga where there is almost no competition, I think MC still has a long way to go, we will have to judge from next season