Vernon was a fantastic fighter, great jab and fundamentals, good power. Unfortunately for him those Mayorga losses put a stop to all the hype he had after beating Shane and his career never reached where it should have IMO. Also remember he had a lot of injury troubles post-Mayorga that kept him out of the ring and IMO he was never truly the same after.
Mayorga was a 6-1 underdog to beat Vernon, and Vernon was a 7-1 underdog to beat Mosley, so I guess officially Vernon/Mosley was the biggest upset.