Gatti would get hammered by Tszyu, easy KO for Kostya IMO.

Sharmba is a toss up, Gatti was a decent boxer and though Mitchell boxed well too Gatti had power and could grind it out too.

Zab had the skill to beat anyone at 140, but he didn't have the drive, desire, or heart of an Arturo Gatti. Gatti would be over matched but he could pull off the upset because Zab could phone it in from time to time. Toss up IMO.

VS Corrales, Castillo, or Hatton I think Gatti would have had better chances because he'd be bigger and those guys would be more apt to be drawn into a war.