Relax, he haven't even played yet and our biggest was Vidal(long term) or Pirlo.
We didn't know how Vidal would turn out then, nor did Pirlo at the twilight of his career. I am not questioning their ability but the interested they generated during the signing and the form they are coming from.
Tevez is definitely our biggest signing in post Calciopoli, one of the top players in his position and definitely WC player. I can only think of Diego who come close to as a high profile signing in this post Calciopoli era.
Tevez signing reminds me the days Moggi signed Viera, Cannavaro, Thuram.