Bony is in a difficult position. As is Pellegrini. If Aguero misses a few games here and there and Bony plays well, scores a hat trick, what happens when Aguero returns to the team? Drop Bony to the bench, or is Pelle tempted to go back to 4-4-2 to accommodate both of them? If he plays 4-4-2, which midfielder does he leave out?
Chances are, Bony goes to the bench, regardless of how well he has done.