It's funny, I thought he defended brilliantly, barring one late moment, as a full back against Chelsea...
In fact, in his limited time at City the only two games he's been suspect at the back were this last one; his first full competitive game in almost a year against new look top opposition; and one last year against Liverpool; against a then unknown to be quite so brilliant Salah. I'll acknowledge he wasn't perfect defensively in the other games, but not so bad every other comment would mention it.
Watch the games against Watford, or Bournemouth, or Feyenoord from early last season and see how little we struggled in his area of the pitch. Because those games will be far more reflective of his upcoming season than this last one. Of course they'll be shaky moments, but do you all really think we'd be playing the way we do if it was as systematically flawed as some of your are implying?