You've seen it all before.......
Chuck Liddell was never the same fighter after the Rampage Jackson fight;
he lost a U-decision to Jardine, won a very close decision over Wanderlei Silva, then called it a career after getting KOed 3 consecutive times to Rashad Evans, Shogun Rua, and Rich Franklin
Now mind you this isn't Chucks fault.......dude has a pretty hefty KO reel himself on youtube, and has been in the fight game long enough to certainly have been "weathered"..
But lets look at other cases....
Andrei Arlovski aka Andrei "Glass-Jaw"vski
And Victor Ortiz as well (no gifs available other then the cheap shot by Mayweather)
Is there a way to enhance your chin by taking a punch, or is it soely based on genetics incapable of altering?