How does one mere match prove Federer was the superior returner to Agassi versus Sampras on grass?
Is Rosol a superior returner on grass versus Nadal than Federer is, by that logic? Do you think over the course of 10 matches versus Nadal on grass (lets say both Federer and Rosol play 10 matches against Nadal), that Rosol would have won a higher percentage of his return games versus Nadal?
It's one match, dude. One match.