Awww but you forget one crucial thing. Federer had chances to beat a pre-prime Nadal at the French Open in 2005 and 2006 and yet failed to do so. Also failed to beat him at Monte Carlo or Rome in 2006, even wasting two match points vs pre-prime Nadal in Rome. So while Nadal has atleast beaten post- prime Federer (if you insist on that) on Federer' surfaces, Federer has failed to do the same thing to a pre-prime Nadal on Nadal's surface.
Nadal was not pre-prime in 2006, at least not on clay. In fact, one might argue he was better on clay than he is today.
Nadal is the king of clay, no question about it. He's far better than anyone on this surface. Federer never got a chance to meet him on his favorite surfaces. On grass they play only one tourney together per year, and on fast hard courts, Nadal never reached a Cincy final, never reached a USO final to face Roger. And in the two TMC matches they played, Nadal was beaten in straight sets. Nadal was not good enough to reach those finals and is only
doing so this year by reaching the AO final and barely beating a post-prime Federer. That wasn't AO 07 Federer in this match, I'm sure even the biggest *******s are aware of it.
Next year Nadal may finally reach some more finals, like USO and Cincy, but Federer will be 3 years past his prime by then. Truth is, Federer was good enough to reach finals on all surfaces in his prime (and even not in his prime) and he did it multiple years (2006, 2007, 2008, 2009), and Nadal, despite being at his peak in 2008-early 2009, couldn't reach finals on all surfaces in one year. Nadal was never enough to reach the USO final, AO final, and more HC events. What about the TMC? How come Nadal never reached a final there?
You can say "weak field" as long as you want, but even if it was, Nadal faced the same one Federer did, and failed.