Harold Johnson against Willie Pastrano, maybe? Johnson had worked long and hard to finally get full recognition as 175 lb champ and was being lined up for a tilt at the Heavyweight title against Liston. In fact, Liston was ringside to watch Johnson's defence against Willie as a way of building some publicity for the prospective fight. Pastrano still had a reputation as a waster who wasn't making the most of his talent, and his form going in to the fight had been pretty patchy. But he ended up getting the upset win, taking the title and scuppering Johnson's plans for that big-time fight against Liston. Mind you, Pastrano boxed brilliantly, so maybe not a simple case of Johnson overlooking him. But still, it denied him that Liston opportunity.