Few sane experts believed Matt Serra could pull off the unthinkable and dethrone welterweight champ Georges St-Pierre at UFC 69, especially after "The Terror" narrowly edged Chris Lytle in the finale of the The Ultimate Fighter 4: The Comeback.
Lytle not only outstruck Serra 195-91, including 42-20 in the significant strikes category, he also scored on one of two takedown attempts and stuffed 15 of 16 shots from the New York native.
Nonetheless, Serra got the nod from two of the bout's three judges, earning a split decision win over Lytle and an opportunity to square off with reigning champ GSP at UFC 69.
Deemed a massive underdog, Serra stunned St-Pierre and the MMA community by scoring a TKO win at 3:25 of the first round.
Although several underdog stories have emerged in the sport since, Serra's miraculous upset represents the most notorious and mind-boggling in UFC history.
Here are the 10 greatest true-to-life Rocky-esque stories in MMA history.