If you are not good at talking about tennis it does not mean that you are not very knowledgeable about tennis.
Yes, but your original point (see above) was that we should respect what people like Sampras SAY ("Sampras said...") over and above what posters like Roy Emerson say. That's talking about tennis, right?
So are you SAYING that maybe Sampras isn't that good "at talking about tennis"?
Either way, I'm confused. Might be because your argument is shit. I dunno.