Doug, do you know why businesses, corporations and even some professional sports teams hire psychologists to administer personality tests?
Because research has found that certain people and certain personalities mesh better in the workplace with one another, and by extension, more production is yielded by finding that balance.
Experience, personality, leadership, these are tangible traits which might not increase the talent level, but they do maximize the ability to perform at said level. It's not that they make someone hit the ball harder, field it more cleanly or run faster... it's that these people are conducive to a better environment where players would be more engaged and likelier to play to their potential on a daily basis.