Most Pro level MMA fighters have insane chins

Something I feel that doesn’t get talked about enough is how insanely durable high level pros are. Some regional pro guys have high level skills, but the durability is not there. Most of these guys get weeded out before they reach a high level by a flash KO/TKO. It is something I feel that is definitely genetic. Sometimes the most technical guy in an MMA gym, is not even a high level pro.