“Noncombatant” is backed into a corner + *forced* to engage in combat, what are their stats?

I can’t seem to find it in the DMG, but if for whatever reason a “noncombatant” is backed into a corner + *forced* to engage in combat, what are their stats? Should is simply use commoner stats? No proficiency bonus in anything? Or disadvantage? I’d use commoner stats

— Mike Mearls (@mikemearls) August 26, 2018