Nick Diaz is back and he’s about to face a world champion. A few months ago that sentence would have caused half of the MMA community to spontaneously combust, but since then the whole retirement/suspension thing has dampened that excitement. Still, even if Diaz is considerably outmatched (which he is), his BJJ super-fight against Braulio Estima proves one thing. Nick’s thirst for competition is still strong. Cesar Gracie can say we haven’t seen the last of Diaz all he wants, but the best evide…