Ah, but the way you wrote it looked like it was a 4-3-3, but my mistake.
I don't agree that Cassano is a better player than Silva btw, even though he is on fire recently Silva remains one of the best attacking midfielders in the world. Silva is a very creative player, i think your underestimating him here, his natural position is a trequartista, so thats a plus too.
Cassano knows the league more which might make him a better option, but i think if Ranieri were to stay as manager, Silva would be the better option because he is perfectly capable of playing on the left of a 4-4-2.