But of course- as they say, there's more than one way to skin a cat. One of the good things about a buckler is its handiness- even when you're wielding one, if a grapple were to occur you could easily transition to meet the challenge. Or, put forth one of your own in the form of a stiff-armed thrust to the general area of the face. You see, it takes years of training and practice to react or anticipate a move like that and not flinch.
Generally, a person who sees something hard and shiny moving quickly towards one's face can shake up even the best laid strategies in a duel. And because it is so lightweight, multiple jabs to the face in tandem with swordplay makes you more dangerous than the longsword man. In my humble opinion.