True. But the argument here is physically knowing 'how' to do something and an having an understanding of how what you're doing works are two different things. I can tie my shoe laces very fast, and have been doing this nearly my whole life. Do I have any knowledge about shoelace tieing? No. If someone asked me how best to tie their shoelaces I would have no idea what to say to them.
Sampras is an 'expert' at playing tennis. That doesn't mean he knows anything about tennis history or understanding statistical trends, or dealing with a myriad of unknown variables.
[mass noun]1facts, information, and skills acquired through experience or education; the theoretical or practical understanding of a subject:
Pete Sampras has high level practical understanding of tennis. Tennis expert is a person who is very knowledgeable about tennis. Therefore, Sampras is an tennis expert.
It doesn't even mean he follows tennis currently!
He follows tennis currently http://www.tennischannel.com/news/Ne...x?newsid=11764
If I wanted an expert on those things I would probably ask a professional gambler, who makes a living making predictions, not hitting the ball over the other side of the net.
But, my point is that every reasonable person will rather believe Sampras than anonymous posters on MTF.