Yeah, he is like so many other guys who wasn't disciplined with his diet, with his training and stopped developing his game at a super young age because he was so talented he didn't really need to...until he really needed to. Kelvin Gastelum was similar, Pettis, Lombard and others. I'd wager in some ways Chandler was similar, he was so talented he didn't really develop his game since about 25-26, relied on his athleticism and never even improved his gas tank.
Sucks, but its how it goes. Guillard just didn't have the mind to actualize his potential.