Will light rehab work help out Sidney Crosby or other hockey player or other player in other sport to return-.?

Concussions are a weird thing, there is no way to predict when or even if they will ever go away. Crosby took two back to back serious blows to the head, so thats 2 moderate concussions right there. You don't want to rush a player back when they have a head injury, it needs to happen on its own.