Collberg is the best example that for the vast majority of prospects, it's decided at the draft. Good pick or bad pick and remember that on average each draft yield some 40ish really good players, so mistakes are impossible to avoid on the long run. The key are not the mistakes, it's how many really good players can you draft outside the top-22, which is around where the hit rate drops markedly. Some teams are terrible at that like Edmonton or Calgar, other like Dallas are competitive year after year because of that.