If the knife guy is moving forward, move to the outside of his knife hand as you draw your weapon, and if need be move left and down to the ground with feet between your trunk and the knife as you draw your weapon.
Now I'm just thinking out loud here. Suppose it's a knife guy (a criminal) against an older concealed-carry citizen. The older citizen doesn't have the mobility to sprint off to one side of the attacker.
What is your opinion of this: Suppose the citizen just drops to the ground as he draws. And by drop, I mean his back ends up on the ground. He might get kicked, but I'm thinking he'd be a bit difficult to stab. And I'm thinking the knife guy might be surprised by the drop move.