Depends on how you look at it I guess. 5 already looks so bad, how would 6 look? And why woudl he beat Nadal this time if he lost the last 5 times? It was just incredibly unlikely, especially given the form Nadal was in going into the FO. And deep down Roger knew that.
I am not saying he wpuld defeat nadal, but there is always a chance. Federer, who has lost to the likes of delpo in the USO, tsonga in wimbly, knows this.
He had also crushed nadal at WTF last year and i think he would have fancied his chances.
Professional players do not tank matches in Grand slams. I think it's kinda insulting to assume that. They just have a bad day.