A problem is what the reasonable limit for a fighter's reaction speed would be. On the subject of boxers, sometimes all it takes is a well thrown punch and they never see if coming. Yet imagine a character like many on this site reaching to draw his weapon in front of a boxer. He'd have little experience in getting punched at every day. It'd be from close range and out of his area of expertise. Logically the boxer could probably cream him in one shot before he gets a blade out.

Yet how many, and be honest now... how many weapon using characters on this forum could avoid that strike? I'd imagine just about every player would say their character would see it coming in time. But if every match could be settled just like that, those unfamiliar with the intricacies of boxing losing out nearly every time under such circumstances, I'd be a regular Chuck Norris.
My main character Gonad is a pugilist of the highest order, but if he won by logical default everytime he got into striking range shit would be boring as hell.

I don't mind a swordsman ducking a left straight that even a trained MMA fighter might not notice. It keeps things interesting. And yes, I know that normally a swordsman would cut an MMA fighter in two. This is just a circumstantial argument about reactions. Sometimes willing suspension of disbelief is what lets us have fun.