As if Vidal couldn't play as AM in a 4-2-3-1. It's all about the manner of playing. Formations aren't about stereotypes, pal. Conte played a 4-3-3 in a complete different manner as well.
Of course he COULD play CAM, just like Marchisio can, so can Pogba probably and even Perayra.
But it's about getting the BEST out of your best players, and if you think taking by far our best defensively capable midfielder, slapping him in a CAM spot in a 4-2-3-1 AND having god knows who on each wing is a viable option, then I don't know what to say.
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Oh and before I forget, 4-2-3-1 means we can say goodbye to Tevez or Llorente
Benching Tevez is unacceptable, and Benching Llorente would be harsh considering he's definitely more suited to playing the lone striker role. So do people want to sacrifice Vidals defensive contributions, and bench one of our strikers to fit somebody like Giovinco/Pereyra in to a 4-2-3-1? Because I sure as hell don't, and thankfully Allegri probably wouldn't fancy that either.