Three things stick out for me.
- The loss of Kompany
- injuries to keeper and backline (especially Laporte)
- Introducing Rodri in midfieid.
The loss of Kompany can't be underestimated, he's been the leader and player embassador for that club close to a decade, he would have been an example and prescence to every single player and it's impossible to replace that overnight.
Laporte, Zinchencko and Ederson all have had medium to long spells out and at different times. It's easy to pinpoint Laporte but where is the consistency in the back four? It's going to be chopping and changing from now till pretty much the end of the season and that's hard to build momentum with.
Rodri, great player but he's different from Fernandinho and offers less protection to the back four. I'd imagine the idea with him in the team is greater possession but just look at how open they've been on the counter this season, the mix still isn't right or needs time to gel.