great fighters with weak chins..

freddie roach is always saying khan has great talent and a suspect him which can be protected. also, he will become a champ if he protects his chin. we all are aware of khan's chin and we noticed the difference under FR with regards to moving, tucking his chin under and cutting of the chance of getting clocked. but surely someone cannot go on to be a world champ especially in LW division without at least taking a few big licks along the way?? so my question is, can anyone think of someone with a chin as supects as khans who went onto great things, or is it a matter of time?