City defence was WAY on the decline last year, this year even worse. Kompany is just getting worse and it's weird because. Sometimes players pick up an injury and it changes their game physically, but as a CB his reading of the game, his timing, everything about his game, he was brilliant for 2-3 years. So even if he's injured he should still have the mental side to the game but he's become comically awful frankly.
Zabaleta is no where near his best, Clichy also gone way down hill, Mangala was highly rated and he's done nothing. If it was purely a decline this year you could put it all on Pellegrini but it was clear they were getting worse last year, I just don't know why. Pellegrini obviously hasn't improved it though which is his fault.
Last year City's offence was so so much more consistent. They've scored plenty this year but it's much more sporadic, longer spells of terrible form, less dominant in more games. Aguero due to injuries and a less good midfield in general doing way worse this year.