The earlier Pep Guardiola knows how weak his defense is the better for his team and his coaching career because the defense are fully exposed this season since the time Rodri get injured.

The main problem Manchester City faced in their past two months was a defensive problem which exposed the team and make them dropped from the first position in the Premier League table to where they are now; they have recovered a bit in their last two matches.

If Pep and Manchester City were able ti sign defenders this January, they will be better than they are right now, and they can still compete for the title race.

Yeah I think you are right. Man City for last few years heavily depended on just only one player ( Rodri). There is no secret that every team knew it, and for this there defense was heavily exposed. But at the same time, I think Pep did not upgrade himself as well as the tactics. The variation of the team combination is not changed through the time, so it can be another reason for Pep's downfall.