Five Biggest Upsets

2 of 6

No. 5: Forrest Griffin-Mauricio Rua (UFC 76)

Photograph By Josh Hedges/Getty Images

Rua was still considered the No. 1 light heavyweight in the world when he rose from the ashes of Pride to make his Octagon debut in September 2006. He was 16-2 and coming off a win over Alistair Overeem, while the much larger Griffin (just 2-2 during the previous two years) was considered little more than cannon fodder. Unfortunately, "Shogun" had suffered a knee injury in training and showed up in the UFC looking sluggish and out of shape. Overwhelmed throughout, he finally succumbed to a rear-naked choke with just 15 seconds left in the bout.