When Matt Serra pulled off the greatest upset in UFC history he was a lovable retread who’d been gifted a shot at Georges St-Pierre after winning the fourth season of the Ultimate Fighter. The whole thing was a gimmick invented to give that season of TUF some real meaning. Serra was the UFC’s first legit Rocky figure, and he even had a cartoon-like New York accent to match Balboa’s own Philly drawl.

History has been flattering to the perception that this was the Biggest Upset Ever in that A) St-Pierre would never lose again and go down as perhaps the greatest that ever was, and B) Serra didn’t win a whole hell of a lot after that. In fact, he went just 1-3, with a one-sided loss to a contrite St-Pierre at UFC 83.

When T.J. Dillashaw pulled off the greatest upset in UFC history over Renan Barao, Barao hadn’t lost in 33 fights over the course of a nine-year span. Dana White was saying during scrum sessions that he was a pound-for-pound great, while Dillashaw — who also came up on TUF — was being cast aside as a capable nuisance. It wasn’t that Dillashaw beat Barao; it was that he broke Barao. Dillashaw would go on to accumulate a bunch of wins, titles and asterisks, while Barao spiraled out of the competitive existence, winning just two of his next nine fights. 

Context factors into figuring out these damn things. You have to look at the beforemath along with the aftermath, the circumstances and the magnitude of the fight itself, and then review all of it from some panoramic high spot to arrive at the subjective heart of the greatest upset of all time. 

Of course, the literal betting odds play a role, too.

This weekend at UFC 269, Julianna Pena pulled off an upset over Amanda Nunes as a nearly 7-to-1 underdog on the book, which many saw as the greatest upset in UFC history. It very well could’ve been. As far as using Vegas odds as a strict gauge for determining that, it was right up there among the most ticket-ripping upsets ever. The only greater upsets were Mariya Agapova’s astonishing (but mostly ignored) loss to Shana Dobson as a -1400 favorite; Holly Holm’s seismic capsizing of Ronda Rousey at UFC 193 as a +830 underdog; and Serra’s KO of GSP, who was a 13-to-1 favorite.

In Holm’s case, there was some debunking going on. Rousey’s “invincibility” was more of a figment of pop culture’s imagination than anything else, as she became a symbol of badassery. She was being booked into hypothetical boxing matches with Floyd Mayweather and many saw her as just a few pigeons shy of being the female version of Mike Tyson. It was a perfect storm of willful indulgence from every media outlet to latch onto her as something invincible, powerful, unapologetic and unyielding. Something larger than life. But then Holm kicked her in the face and the all those flights of fancy crashed to the earth with her. 

In the moment it felt like the most ape-shit upset that ever was. Time has taken away some of the magnitude. Especially since A) Rousey was a shell of herself when she returned against Amanda Nunes 13 months later, which made her seem vastly overrated in retrospect, and B) Amanda Nunes made people forget about their sinful indulgences with Rousey. 

To this day I’d argue that Michael Bisping’s upset over Luke Rockhold at UFC 199 was the greatest. Do I really believe this? Maybe…on some days. Maybe I’m willing to argue this case because the circumstances were so stacked against him. Bisping had lost to Rockhold 18 months earlier without a lot of resistance, which didn’t really give him much reason for hope in a rematch. He was already somewhat legendary for coming up short. Every big fight he was in, he lost. He was blind in one fucking eye. A pirate in that way, fooling commissions. He wasn’t training when they called him to fill in for Chris Weidman; he was drunk at a basketball game in Canada. 

And Rockhold was a beast. He’d lost just once in seven years, and that came during the TRT Vitor Belfort days, when the UFC was dropping sacrifices to a lab in Brazil to keep the monster sated. It was Belfort, by the way, who took Bisping’s eye during that same year.

Bisping answered the call though. He won. He knocked the 6-to-1 favorite Rockhold out cold. He did the unthinkable. 

Same could be said for Pena. I didn’t see a good path to victory for her, even if she herself was telling everyone who’d listen that she had one. We’d seen Pena come up short plenty in the last few years after talking a big game. Valentina Shevchenko had submitted her, so had Germaine de Randamie. Going way back, Sarah Moras beat her, too, which isn’t an indicator of a live dog. Pena hadn’t fought all that often, and some of her victories were unspectacular. 

Really, though, when talking about a great champion, it’s oftentimes hard to foresee the overthrow. Pena was incidental in this matchmaking. Wasn’t she just the next one on the conveyor belt to be devoured? Nunes was a two-division champion who’d created a gulf between herself and the next nearest competitor in both weight classes. She had already beat Valentina twice. She destroyed Rousey and Holm. She had knocked out the great Cris Cyborg. The broadcast showed Kayla Harrison in the crowd in Vegas to plant the seeds of a superfight with Nunes, because who else was there to cast doubt on Nunes ever losing again? 

It wasn’t inconceivable that Pena could win, so much as it was that Nunes could lose. That’s what makes the odds so long and the feat so big.

And so it was that Pena ended Nunes’ bantamweight reign. She ripped through her and, as a historic happening with so many millions of witnesses tuned in to watch it live, there was an overwhelming urge to call it exactly what it felt like: The greatest upset of all time. 

After the dust settles the only question becomes, was it?