Too little information, esp. when I am hearing the voice of a translator, but while he does strike me as an introvert, lack of interest in a legacy and stating that he believes the sport is 100% mental strikes me as inconsistent with his being an ISTJ.
If you put a gun to my head and asked me to type him based solely on what I am perceiving from this--and I am almost totally unfamiliar with him--I'd go with INTP. But I'd have a high probability of being wrong.
He went to art school and can apparently sculpt, draw, paint, etc.....
I'm pretty sure he is at least an IST....but ISTJ because of dedication and motivation to train. Defiantly not an ISF...or an INF quite possibly could be an INT but i doubt it. I get a very IST vibe from him though.