This is the problem that Nadal will now face. Any time he was in trouble, he had a go-to neutralizing rally shot, from which he knew Federer could not hurt him, or could not dictate play from. That is turning into a no fly zone for Nadal recently, so much so, that he changed his tactics to AVOID going into that shot, as crazy as that sounds. As soon as something like that happens, you are in a world of hurt. Nadal cannot use the defensive or rally slice against Federer the way he does against Djokovic, Federer loves the low ball, and would likely step in and smack a backhand flick winner from it.
He will need to vary that serve, lots of body serves, but Federer is picking up those shots more and more from him. The only way I see is for Nadal to become more aggressive than Federer, and that is something he will never be comfortable doing, it is not his natural game. His diminished movement makes him weak to that inside out forehand or cross court backhand into his forehand side, a game play that Djokovic showed the world. I am interested to see how Nadal tries to combat THIS Federer who clearly seems to be mentally free from the shackles that plagued him.