Can a non-Force trained human wield a lightsaber proficiently?

If someone was incredibly well trained with a regular sword, but had no connection to the Force, would that person be able to wield a lightsaber?

Are there any examples of this or something similar to this in any canon?

I don't know if a Jedi's / Sith's connection to the Force enables them to use a lightsaber, or just increases their abilities with a lightsaber.

I guess Grievous is the obvious example of a non-Force user being pretty badass with a lightsaber, but I'm looking for a regular human here.