I only just realised this thread was "Brett" Prismall, bit slow.
I reckon if he stays at Geelong next year we'll give him a run in some pre-season games and see how he goes, he still has wrist/arm problems I believe.
If he's fine and plays well I can easily see Shannon getting dropped for him, not a direct swap though, we'd have to rotate him in/out of the midfield I guess.