It is easier to evade a jab than a knife. Your opponent will have an advantage also in length, he will reach when you will not. This sounds like a training scenario, he attempts to stab you and you may react to it. In real life you can hurt his arm, punch him as hard as possible but his mind is still set on killing you. This means he is most likely in a frenzy and pumped up with adrenaline. All rules are out in such a fight, even in a painful submission grip on his arm you will see that he might even break his own arm just trying to stab you fatally. A broken arm does not mean he has been stopped.
Once more, a knife fight is dangerous and fatal.
Are you advocating going on the offense against a knife wearing opponent? Then you need the following to apply, that he does not wish to stab you. In any other scenario he will do that upon your entry, at least for self defense. Noone will pull out a knife, challenge you to a duel from a good distance and then talk **** about your family before attacking. If they intend to use the knife they will walk up, pull out a knife and stab you as many times as possible in as little time as possible and then walk through you and leave.
