I think it's obvious that Yaya is still vital for us in possession, but defensively it leaves us exposed when we don't have the ball. I don't think the 4-4-2 is the problem because when you play a 4-3-2-1 with Yaya there is still the defensive problems. This leaves Pellegrini with a dilemma. I think it's more of a time for a change of position for Yaya.
It might seem crazy, but I'd put him on the wing in Nasri's position and play Fernando and Fernandinho in central midfield. If you look at Pellegrini's tactics for the 4-4-2 the two central midfielders are more defensive minded and protect the back 4. Something Yaya currently is failing to do. The two so called wingers are inverted and come in centrally ala Silva and Nasri (unless he plays Navas). The width is created by the fullbacks.
When you watch us play Silva and or Nasri are always dropping back when we are pressured and want play out from the back to help start the attack. So essentially playing out from the back it would be more like...
_Aguero__________Bony_
_______Silva______________
____________Yaya__________
_Fernando __Fernandinho_
If Yaya has the ball he can find Silva in space or play the long ball to Bony or Aguero.
When we are pinning the opposition in their own box he would go out wider linking up with the full backs and/or switching and linking with Silva the way Nasri does. This would essentially free him from his defensive duties while the 2 Ferns protect against counters.
Again it might seem crazy, but Messi plays on the right wing for Barca, James Rodriguez plays out wide when he's a no.10. When you think about it Silva and Nasri aren't wingers as well.
