the clues -
links to Japan - Tokyo 64??
use the setting in training - the track and athletics??
You're a kiwi so I'm going to say it was about Peter Snell? but havent any idea who said it.
Unless it's about Joe Frazier - but I'm not sure that you use the ring as a setting in training unless Doc has some new ideas!
Yip, Huggy Bear is nearly there, it was Peter Snell taking out the 800 and 1500m double on the athletics track.
All we need now is the coach who said it?
With this tip it should be pretty easy, the coach has had some influence over Doc