Double Naught Spy
Sus Venator
If you've let someone get close enough to get a hand on your coat you've done something terribly wrong already.
Apparently, you are a hermit living in an isolated location and are self sufficient. Either that or you are just as guilty of having done something terribly wrong countless times in your life. You cannot attend a movie, go shopping, attend church, attend college, or otherwise participate in a normal life without people getting close to you regularly.
You will instinctively know whether you can take somebody in a hand-to-hand fight, whether you should fight or run.
Really, what instinctive insight do we have about the aggressor's skills and capabilities?
Well, how long would you recommend pondering the issue while someone is trying to stab you? The immediate instinctive decision is the one to go with.
The scenario presented doesn't have the bad guy trying to stab you yet. There may actually be considerable time (several seconds) to ponder responses. You may go with your instinctive decision, but your instinct doesn't know if you can take the bad guy or not. Note that your instinctive decision may be very detrimental to your survival. Folks like to talk about Fight or Flight, but there is a 3rd F instinctive decision, to Freeze. I happens with considerable regularity.
So, in this case, I would try to control the knife hand, and start stepping backwards. As the perp leans forward and loses his balance, then I'd go from there.
Keep in mind that the BG doesn't always approach from the front.