I think the most amazing thing about this performance is that Robredo didn't really have to play that much out of his mind.
All he had to do at points was get the ball into play and watch Federer choke. I'm sure Fed has lost to lower ranked and less glamorous players, but at least he managed to take them to more than 3 sets and they probably played out of their skin. For Fed to choke this much... it's just not feasible.