mmm
Out of the last 10 sets between them, Hewitt has won 1. And 2 from the last 17. I would say that 3-0 is about 55% likely from this and their relative form.
The problem is that Hewitt is basically a counterpuncher. So against big servers like Roddick he can cause trouble. Federer can play in a lot of different styles, that's why he is the best since Borg.
Against Hewitt there is no reason to serve flat out, that's what he wants, gives him more pace for the return. No, ease off the gas and put lots of spin on the ball. Use placement to make him stretch on those returns. Easier said than done but not for Federer.