Upsets have been happening ever since fighting has been around. Anything can happen to anyone in a fight. Although there have been many outcomes that could be considered upsets, two really stick out above the rest. The first is Georges St. Pierre losing his title to Matt Serra. The second, happened this past weekend as Anderson Silva lost his title to Chris Weidman.
This leads to the question in the title. Which upset could be considered the biggest? First we need to breakdown each fight to understand why they were such huge upsets in comparison to others, and then we can make an informed opinion on which upset had a greater impact on the MMA world.
Let's rewind back to the early to mid 2000's when Georges St. Pierre burst on to the UFC scene. Matt Hughes was the dominant Welterweight Champion and considered the best Welterweight fighter to ever live. Georges was 7-0 with 6 stoppages at the time he got his first crack at Hughes and UFC gold. He had wins over Ivan Menjivar, Thomas Denny, Karo Parisyan and Jay Heiron. As we all know, Hughes did defend his title against St. Pierre by way of submission. But it was what happened after that fight that made the Serra fight so unthinkable. St. Pierre went in a rampage winning six straight fights with three stoppages. These fights included a domination of Jason "Mayhem" Miller, a submission over Frank Trigg, a TKO over Sean Sherk, a decision win over UFC great BJ Penn and a TKO victory over Matt Hughes in a rematch that saw GSP secure the Welterweight title.
St. Pierre looked untouchable. Matt Serra on the other hand did not look to be the person to take the belt away. He was coming off of a split decision over Chris Lytle on the Ultimate Fighter 4 Finale and before that he lost to Karo Parisyan. St. Pierre entered the cage, followed by Matt Serra. What came next shocked the mixed martial arts world. Matt Serra caught St. Pierre with a good shot that dropped the champion. The follow up finished the fight. Matt Serra had coke back from an uncertain future with the UFC, to defeat the welterweight champion.
I don't think anyone in the world saw that as a normal occurence. I am sure that deep down, Matt Serra himself didn't expect to go into that fight and stop Georges St. Pierre.
Now, lets switch gears and talk about arguably the best fighter to ever live, Anderson "The Spider" Silva. Silva came into the UFC and immediately cemented himself as a great fighter. He was so impressive in his debut stopping Chris Leben that the UFC gave him a title shot in his next fight. He went on to dismantle Rich Franklin snagging the UFC Middleweight championship. His run after that was unmatched. He held wins over Travis Lutter, another Rich Franklin victory, he stopped Dan Henderson, Nate Marquardt, Yushin Okami, Vitor Belfort and Chael Sonnen twice. His run also included wins over Thales Leites, Demain Maia, Patrick Cote and wins at Light Heavyweight, a division above his weight class, over James Irvin, Forrest Griffin and Stephan Bonnar. He had finished 26 of his 33 victories. He had defended his Middleweight belt a UFC record 10 times, had never lost inside the octagon and had never been KO'd in his career as a professional fighter.
Chris Weidman on the other hand, although undefeated, only had 9 total professional bouts. That's right, Silva had more UFC title defenses than Weidman has total fights. Weidman was picked by any to dethrone the champion due to his size and style of fighting. But I am not sure how many people really believed they would see the great Anderson Silva do down that night.
Then it happened. Weidman caught Silva clowning around in the 2nd round of their 5 round title fight, and Silva didn't recover until the fight was called off by veteran referee Herb Dean. The best fighter in the world, had been knocked out by essentially a newcomer to the professional mixed martial arts world.