Jon Jones' first big UFC test came on the undercard of UFC 100

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On the undercard of UFC 100, there was a 21-year-old prospect making just his third appearance in the Octagon. That man was Jon Jones. After six professional fights in a span of three months, Jones made his UFC debut at UFC 87: Seek and Destroy. He defeated fellow UFC newcomer, Andre Gusmao via unanimous decision before going on to secure a decision victory over The Ultimate Fighter alum, Stephan Bonnar.

Getting the call to appear on the undercard of the landmark UFC 100, Jones was booked against Jake O'Brien. At the time, O'Brien had only lost to Andrei Arlovski and Cain Velasquez. This would be the toughest test of Jones's young career.

The first round of the fight played out with O'Brien stalking Jones and using his boxing to control the Octagon. Meanwhile, Jones used kicks and footwork to try to maintain distance. The second round started in similar fashion before Jones feinted a takedown then bounced a spinning elbow off the top of O'Brien's head. It was the beginning of the end.

Smelling blood in the water, Jones began to pressure the wounded O'Brien. Retreating for the first time in the fight, O'Brien shot desperately for a takedown which Jones easily stuffed. Jones locked in what is now called a ninja choke to force the tap and earn his first stoppage victory in the UFC. The commentators didn't know what to call the choke, referring to it both as a modified guillotine and a no arm d'arce.

Watch the full UFC 100 fight between Jon Jones and Jake O'Brien

The submission was the first of 12 finishes in the UFC for Jones. It was also the last time he would leave the Octagon with an undefeated record.

Just over four minutes in to Jones's next fight he would be disqualified for illegal downward elbows. Up until that point he had been dominating Matt Hamill. In a career highlighted by multiple championship runs, the disqualification loss still stands as the lone loss on his record.

Despite having arguably the greatest resume of any individual to ever compete in mixed martial arts, Jones's career is also a story of what could have been. It is well documented that when Jim Miller faces of against Bobby Green on April 13, 2024, he will be the only fighter to have competed at UFC 100, UFC 200, and UFC 300. As the only other fighter from UFC 100 to have competed in the promotion this decade, Jones easily could have matched that feat.

Jones was riding a 12 fight win streak and had successfully defended his title eight times before having his belt stripped by the UFC for fleeing the scene of a hit and run, He would go on to serve a six month suspension, during which time rival, Daniel Cormier, won the championship. This set up a title rematch between Jones and Cormier for UFC 197. However, three weeks before the fight Cormier had to withdraw with an injury. On short notice, Jones defeated Ovince St. Preux for the interim light heavyweight championship.

The championship unification bout between the bitter rivals was scheduled to headline a star studded UFC 200 card. In a now iconic video, three days before the fight, Dana White informed Cormier that Jones had failed a drug test and was no longer able to compete. Instead of headlining the biggest card in UFC history, Jones was serving a one year suspension.

Jones returned from his suspension to defeat Cormier and reclaim his belt only to have it stripped again after a failed drug test. After another suspension and with Cormier off to heavyweight, Jones reclaimed and defended his light heavyweight belt, with no real closure to their rivalry.

Years later, Jones made the move to heavyweight, defeating Ciryl Gane for the championship. Declaring his intent to retire after defending the belt against Stipe Miocic at UFC 295, a torn pectoral tendon forced him from the bout. Had he not been injured and despite his stated intent to retire, it's hard not to imagine Jones headlining UFC 300 before calling it a career. Like so many times in Jones's career the fans are left thinking what could have been.