Believe me, it is great athletes that make a coach great. If an athlete has no talent it doesn't matter how hard they work they will not excell. Combine a great athlete with a knowledgable coach and you have a great coach.
Case in point: I know of this situation from a friend who coaches.
He has coached State Champions and other very successful athletes- sub 1:55 800 runners, regional championship teams, etc.
He has a girl runner who runs 5-6 miles per day to prepare for the XC season. Does cross-training with a personal trainer. This poor girl has no talent what-so-ever. She can't run 8:00 per mile for a 5K road race. Her body is not built for any sport (ok, maybe curling or bowling). She has no leg lift what-so-ever and no push off with her toes as she runs. She is big for a girl- tall, big thighs, real big feet.
She has teammates (girls) who can break 19:00, 20:00, and 21:00. The team is successful and has rarely lost in the last four years. Yet- her father complains to the AD that the team needs a new coach because the coach is bad because his daughter is slow. Also, the coach should put his daughter on varsity so she can prove how fast she really is. Keep in mind that this girl has a PR of 6:18 in the 1500 and has never broken 25:00 for 5K.