The thing is--against Nadal, even a lead is not safe for Roger. He will still choke even on points he controls and Nadal knows this. He will grind out rallies and win this set on grit as Federer starts to overhit because he senses he might win the set. It's an old dynamic with these two until Roger does something unusual to change it--or Rafa plays a bit off (which he never does against Federer