I think if he has the skills to throw a ball and not only make it hit something but throw it in such a way that it comes right back to him every time, then he has the skills to handle around the spikes and throw it hard enough to really hurt.
Besides its not like theres a library or a class for proper speech ettiquete in Besaid. What else is he gunna do besides practicing with the Blitzball?
That being said I dont like over the top religious nuts, but if everyone had the mysterious, silent, cool, personality then it would get rather predictable.