Pete Sampras was a top professional player in tennis for a long time, so it's logical that he is very knowledgeable about tennis.
No it is not. My ex was a professional hooker for a long time but she weren't no expert on human biology. She even gave a crap blow job.
Point is, you can be good at doing something without being good at talking about it. You can "know" how
to do something as in being able to do it, without being able to explain
how you do it, or knowing anything about anybody else
who can do it.