Last year Van Dijk didn't get injured. That was where Liverpool were lucky. However, Gomez was on a great run then broke his leg against Burnley. Lovren proceeded to get injured and then Matip which left Liverpool shoehorning Fabinho in as a Centre Back for a few weeks.
Laporte is class and was a leader at the back. Once injured coupled with Kompany leaving things were going to be a bit shaky there. Norwich really exposed City and highlighted Laporte's absence but still had to score 3 to win. Against Wolves I'm not sure what happened. Granted, the defence was all over the place but it doesn't explain why there were no goals the other end. KDB was missing and is also world class but he was missing for most of last season and that had f-all impact.