Hello,
Anyone who trains with a knife in a realistic situation will have been cut and expect to be cut. No matter how skilled one is with empty hands or even with a blade, when facing someone else with a blade it is most likely both will be cut.
If one is to survive an edged weapon encounter then one must accept that they will be cut. You must mentally prepare yourself for the fact your will be injured and be ready to fight on no matter what. For most the shock of being cut is what stops them, they are unprepared for seeing their own blood and fighting through the pain. Unfortunately, there are few options for preparing to fight after one has really been cut so it is impossible to predict how one will respond in a real situation. All one can do is train as best they can, but IMHO spend as much or more time on mental preparation and visualizing being cut and still fighting on no matter what.
The video seen in many LE training classes is titled "Surviving Edged Weapons". It featured Dan Inosonto (sp?) as well as Tuhon Leo Gaje. What the video showed is that if a knife weilding attacker is within 21 feet it is highly unlikely that an officer will be able to draw and fire 2-3 times before he is cut. In some instances both the attacker and the officer will both be injured for real, but the point being that the knife weilder will most likely reach and strike the officer. The 21 feet is seen as the minimal safe distance for facing an attacker armed with an edged weapon which will allow the drawing and firing of a holstered weapon.
On another note, slashes, while deadly, rarely result in death. The more dangerous is the stab, even if it does not appear to be bleeding much, as in many cases the bleeding is internal. Also, a small blade is all that is needed to penetrate to most vital targets, 3" is more than sufficient to kill.
One technique which is particularily dangerous is commonly referred to P'Kal and involves catching the limb with the blade down. If this is successful then the opponent will further injure themselves if they attempt to pull away. Of course the one with the knife can also pull the blade towards themselves as well.
A skilled knife fighter will be able to manuever the blade with a speed and flow akin to Chi Sau. If blocked they will redirect to another target.
All in all better to avoid if at all possible. If not, expect to get cut and have to fight on. FWIW one technique taught to me in the military involved taking a cut\slash on the outside of the forearm in order to get close enough to deliver a killing blow. Not saying this is such a good idea, but it does stress the reality of being cut in a real fight.
Oh, not to be picky, but the chances of coming up against a skilled knife fighter are pretty good, imho. Anyone who has been to prison or grown up on the streets will most likely be pretty proficient with using a blade.
As I like to tell my students, when I used to teach, "I cheat". Rest assured that those you encounter on the street will also "cheat". It is highly probable that you will not even see the first strike but jus feel the results. If you are not ready for that mentally then you will most likely not survive. Also, even if you survive you may be maimed in some way.