I was never a huge fan of the Sandman. He was fairly botchy, and he heavily relied on weapons which is why he was successful in ECW. But this is WCW, where Rey Mysterio first made a name for himself. His WCW work is great, especially his matches against Dean Malenko, Chris Jericho and Eddie Guerrero. Rey Mysterio is a former World Heavyweight Champion. It doesn't matter he was booked as an underdog champion, the fact is that he won a World Title, winning it off Kurt Angle. Whichever way you look at it, it's still a huge accomplishment.
Mysterio would win this easily in a 6 minute match. Sandman isn't very big, so it's not like Rey is truly outmatches here in terms of power, size and strength. This is an easy first round match for Rey Mysterio.