Once upon a time I was a pretty decent table tennis player. At one time or another I was my state's junior (under 18) and Over 40 state champion. Not simultaneously, of course.
I have not played in a number of years due to a knee that is roughly three times the age of any other part of me. I haven't even touched a paddle since, oh, 2004. I also used to be a pretty good coach - sanctioned by the US governing body for table tennis and everything. I still have the card to prove it: says "Certified Coach" right on the damn thing.
Why do I bring this up? A voice (or, more to the point, a keyboard) from the past contacted me the other day. We had corresponded back in the day. He wanted some ideas for promoting his club. (I still need to get back to him on that...)
In the course of the conversation he mentioned a specific style of play with which he had trouble. I asked a few questions and gave him some advice. He came back yesterday, ecstatic. He had beaten some players he had never beaten before, using my advice. So without ever seeing him or his opponents play, based on a couple of lines of chat, I was able to successfully coach him.
The kid's still got it!