Many times you will have only one working eye. It will be covered by something you have to carry or blocked by blood or a swollen cheek. To learn to move in this manner close one eye and have two or more people come at you and you with your hands at your back simply walk to evade. The people coming at you do not sway out of course to learn to keep to their own movement and not be dragged into yours and you need to see and decide which open space between you, you want to take.
Another point is where the partner holds the knife. If it is on his body he is likely to be calm and focused on his job, A knife half a way from the body is usually guarding the space close you the person and shows some fear and an outstretched hand usually means full aggression and no regard to personal safety. This is of course a generalization but take this too into account.