The stuff thats 'secretive' isn't how they train. Its all the same, but what they are training. I mean if you were a pro would you want others to know what you're working on your game to make better so others can get an edge on you and know whats coming? Well to me thats kinda Rafa's case in a way.
The only secret that no one knows about is Djoko's supposed "I'm playing awesome in 2011 because of my gluten-free diet" BS haha