who the fuck are you? Capello?
I see no reason why a two man central midfield with Pirlo playing alongside a purely defensive minded midfielder wouldn't work. Pirlo is no less a defender than Cesc for example, who had no problems playing alongside Gilberto in the olden days, or Flamini later on. While it would be ideal for Pirlo to have two hardworking players in front of him doing the dirty work, so he can be free to play the deeplying playmaker role without thinking too much of defense, i really don't see why he couldn't manage in a midfield duo of him and say, Melo.
Huh?