Brady: I'd be surprised if he plays more than one, maybe two series. But it's decisions like this for which BB gets paid the big bucks; to weigh the risks, advantages, team needs, etc.
I'd also be surprised if BB's doing anything but seeing how Hoyer and/or Mallett handle the offense; I doubt he'd be showcasing either one at this stage, but just being sure they're ready. Maybe his agenda would be to showcase Mallett in game four, where Brady's play is usually limited, if he feels things are otherwise in good shape.