He is an all or nothing player. He doesn't really effect games unless he is scoring or assisting. He doesn't help us control the tempo of the game like Silva can or even like Toure does (or at least tries to do). He is a final third type of player, a final ball sort of player. When he final balls aren't met with goals or chances, or when he isn't scoring himself, his output looks fairly non existent.
He's the sort of player who can have a stinker but come away with two assists. He rarely has a blinder yet has zero goal assisting stats to back it up.
At home, we commit more men forward, and the opposition also sit a little deeper so we have more bodies in and around the penalty box. He is in the final third more often where he can set up goals. Away from home, we fail to gain the territorial advantage which would allow us to pen a team inside their own half for an extended period of time. We started off last night like we could do that, and De Bruyne looked bright, but that only really lasted for 15 minutes.
On top of that, he doesn't retain possession well. Everything he does is almost designed to make a visible difference, so with that comes a risk of losing the ball. If he is only getting on the ball every 5 or 6 minutes, 2 or 3 misplaced passes or a piece of poor control can lead to him becoming withdrawn from the game.
Personally, he needs to play more narrower and closer to the ball players in our team (Silva and Toure). Let the full back become the width. That way he will get on the ball a bit more than he is. From there we can gain some form of territorial advantage and attempt to pen the opposition in. On top of that, considering we are unlikely to replace Yaya this January, we need to help him and channel some of our transitions through Delph and Fernandinho. Because Yaya is so obviously our pivot in midfield, the opposition can double press and close him down before he is even able to turn with the ball. This leads to us losing the ball in our own third and can lead to extended periods of play where none of our attacking players even get on the ball. As a result, Silva drop deeper and isolates Aguero.
As with all top quality attacking midfielders, the key to their performance is down to getting them on the ball in the final third. At the minute we are relying on one player to turn possession in our own third to possession in the final third (Yaya, or at a push Silva, if he drops deeper). We need our other two central midfielders to contribute with the ball. For all their tenacity and eagerness to intercept, we need more from them with the ball.
For me, Pellegrini falls into the trap that many others do where he believes Yaya needs covering with 'legs' when in reality he needs to be playing alongside 2 other ball playing midfielders. If he is such a liability when we don't have the ball, we need players who are capable of retaining it under pressure. At the moment, we only have about 4 in our standard starting 11. I'm sure we'll get the other 7 when Pep gets here.