Four years ago, on July 6, 2013, Chris Weidman pulled off one of the most shocking upsets in UFC history. 

Taking on longtime middleweight champion and consensus pound-for-pound GOAT Anderson Silva at UFC 162, Weidman faced a seemingly impossible task. Silva had won 17 straight, earning a finish in 15 of them. He was the UFC's longest reigning champion ever--a distinction he still holds today (albeit now in a shared fashion with flyweight king Demetrious Johnson). 

He was the sport's most feared fighter, a phantom who could end the fight with one flick of the fist or hips. If need be, Silva would also flex his Brazilian jiu-jitsu black belt. 

He fell to the canvas with a deafening thud. 

In Round 2 of their main event showdown, Weidman found the elusive crack in Silva's striking defense, using the Brazilian's bravado against him. As Silva clowned and feigned danger, Weidman chucked a devastating left hook that landed on the button, putting the champ down and out for good. 

To this day, it remains the only time in 43 career professional MMA fights Silva suffered a knockout due to head strikes. 

The finish also sparked a downward turn for Silva's career. He followed up that defeat with another gruesome loss via leg injury to Weidman at UFC 168 then defeated Nick Diaz at UFC 183 only to have that win overturned to a no-contest due to testing positive for drostanolone and androsterone. 

Back-to-back decision losses followed--one to Michael Bisping and one to Daniel Cormier--then, most recently, Silva got back on the winning track with a close decision victory over Derek Brunson at UFC 208. 

While it's impossible to pin this all on Weidman's ferocious left hand, it is clear the Long Island native singlehandedly altered the trajectory of MMA history that night in Las Vegas. 

Relive the fight with commentary from Jon Jones and Urijah Faber right here. 

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