I think people's perception is too flawed when they react to each players' performances right after the game. I didn't see the Liverpool one, so downloaded it and watched the game with calmness (and being sober!). already knowing the result, sometimes even reverting the play, and what I thought was he was very good in the first half actually. For example, played a wonderful through ball to Silva who then put the cross to Sterling (and Aguero), when both were fouled in the box via red card offences.
Then yeah, he seemed to be in a hurry to play the vertical pass in the second and fucked it up oftentimes, which is a shame indeed, but let's say Otamendi would have had his first and second half performances switched, his thread with 'motm' messages wouldn't bee as much bumped. And back to Kevin, yes, he looked knackered in the second but still managed to play that one killer ball and almost scored the deciding goal.
In any case, it's just a bit pointless to debate his role now as it's true what the above poster mentions: there is no alternative for him and we can't really afford currently to leave him out (this applies to Silva even more, of course). Hopefully it's all in the mind and he'll get back to his best soon enough.