Harry Potter becomes a Quiddich coach in The Half-Blood Prince and does a decent job. I found his tryouts somewhat uninspiring; he should have brought a practice plan. Choosing his keeper based on five penalty shots – an extremely unreliable sample size – was asking for trouble, but it worked out in the end.
Before the first match, I thought Harry was setting up Weasley to be Rafael Palmeiro. However, tricking his keeper into thinking he had taken performance enhancing drugs was quite the ruse. A lot of sport is mental as opposed to physical; sensing that Ron was prone to negative self-talk, Harry employed his mental training skills to help that particular student-athlete play to the best of his abilities and deliver the win for his team.