It's not all down to injuries its just a combination of things all going against us at once not allowing us to get a run of form going for long. Injuries is probably up at the top of the list though, we've never been able to have a settled team which is kind of important(look at Leicester they know their best team and stick to it and it works) everyone's been in and out of the team the moment we look like we could be turning a corner.
We should do a list of things that are going wrong for us to explain why we keep having these dips in performance.
For me its:
1)Injuries
2)Over reliant on key players, when Kompany, Aguero and to some extent Silva are out it doesn't take long for the team to stop playing their game.
3)Aging players not keeping up with the demands(lots of games), Yaya, Demichelis and Kolorov
4)Managers team selections, especially against rapid teams.
5)Manager leaving it too late for tactical changes
I can't believe people are doubting Silva personally though I think he's been playing through injury, he was having a great season up until his spell out it can't be just a coincidence.