At this level managing and coaching is overrated. See Joe Torre and Bobby Cox and let's not forget how Leo Mazzone forgot how to coach pitchers when he left Atlanta.
Yeah there are guys out there that are just as good as the talent they have, but we can't discredit the fact that there could be coaches out there that actually DO have an impact. It would be a hard process to discern which ones they are, though. By no means are coaches/instructors a cure all.