Yaya for me... is more and more "out of gas" - unable to move quickly into position whether on attack or needing to press/cut off passing options.
He remains capable of killer passes though - and so might play a Pirlo role if given protection. But that doesn't seem to be the way Pep plays.
So, for me, Yaya, is past his prime, and will make appearances only in dire circumstances or in meaningless games/games we have won.
And I don't think this is down to attitude - Yaya seems to care deeply about winning - but, either he's simply unable physically to play as Pep wants or hasn't trained sufficiently to get into shape - either way, Yaya isn't an asset to our side on the pitch currently.