Three things about "facing a fast puncher" - one, you won't catch their punch. Two, there is a bigger element here, that is, understand how to handle the whole situation, i.e., you are faced with a fast striker. Don't play their game. Three - at a technical level, since you won't catch their hand, don't try - Seagal does do something nice here, he goes for the bicep in his parry instead, This si a good strategy. Actually, anywhere above the elbow is usually fine, because while the fist is traveling a "great" distance, the upper arm is not, and the elbow isn't really either, at least not that much. So if you connect there, and you will be able to (that's the point) you can then slide down and catch the fist or hand for, say, a kotegaeshi, or even stay higher and go to a different tehcnique.
This is one side of the technical approach.