Coaching level versus playing level
Does one need to be a top player to be a top coach? The question often comes up, and there's an easy answer. No.
However . . . and this is a big HOWEVER . . . it's very difficult to become a top coach without being a top player first. It's a matter of opportunity. If you are a member of the National Team, you train for many years with other top players and work with the best coaches in the country, and if you are paying attention, you gain the experience necessary to be a top coach.
It's possible to be a very good basics coach, one who can train new and intermediate players very well, without being as experienced working with top players. But the key problem to watch for here is that many coaches who teach basics teach them in a way that will later hurt the player. For example, some hold back on teaching the loop, especially the backhand loop, for so long that hitting becomes ingrained, while looping never becomes comfortable. Or they have the player use beginner's sponge so long that their development is held back because they develop a game around beginner's sponge instead of a modern game based on modern "super sponges." So even coaches of beginning and intermediate players need to have enough experience with top players to see what they are doing so they can teach players a foundation that leads to what the top players do.