The '86 WC finals series against the defending champion Lakers could have made the list. They were considered a team of the future, but too young, inexperienced, and without a starting caliber point guard... matched against the legendary (even then) Showtime Lakers. A stunning upset in an atmosphere that even had a notorious Houston sports writer picking against them.
This is not really a upset, more like misleading. First Jordan's bulls retire and scattered. Second that year was the lock out year and they only played 50 games. Third Miami as a 1st seed played NY 8th seed. During those years NY was known for beating Miami in the playoffs, it was Jordan's bulls that gave them a problem. Only one year NY lost because key players was suspended. Its like Rockets 1st seed playing Jazz 8th seed if you know what I mean.