When Hughes did it he played an authodox 442 with Petrov as right winger.
Mancini is playing 433. Where Petrov is one of the forward players. This means we are not looking to get balls into the box as much in terms of crossing, espcially as before today we have had no real height in the box. Petrov is looking to come inside and link up with the attacking midfielders and the central forward (Tevez).
While this is good going forwards there has to be defensive balance and so he has defensive duty on the right. This gives the impression he is playing more on the right hand side than he actually is. I think, although he scored the 433 lost something with Ade in the side. We looked better with either Bellamy, SWP, Robinho playing as the other one of the three.
In a 442 the Ade and Tevez works a lot better, which is why we kept switching it about today. That left Barry on the left and Petrov on the right which isnt ideal.