The unimaginable materialized for Matt Serra at UFC 69 in April 2007.
Granted a title shot on account of winning The Ultimate Fighter Season 4: The Comeback, Serra, a heavy underdog, scored a shocking first-round TKO win over once-beaten welterweight champ Georges St-Pierre.
But in a ironic twist of fate, Serra's win—rather than catapulting the New York native's career—ultimately set off a series of events that led to the meteoric rise of "GSP."
Since his setback to Serra, St-Pierre has won an astounding 44 of 46 rounds, narrowly dropping a stanza each to Jake Shields and Carlos Condit in five-round title bouts at UFC 129 and UFC 154, respectively.
His divisional supremacy even has the UFC's brass chattering of a superfight with pound-for-pound kingpin Anderson Silva—even though GSP has cited that a size disadvantage could dissuade him from accepting the bout.
So with surging former two-time NCAA wrestling champion Johny Hendricks on the horizon, St-Pierre will instead look to add a fourth, current top-10 UFC welterweight to his prolific list of victims.
If St-Pierre happens to defend his belt for the ninth straight time in his upcoming bout against "Bigg Rigg," then do any of the UFC's remaining ranked 170-pounders have the chops to dethrone GSP?
Aside from Tristar Gym teammate and third-ranked Rory MacDonald, St-Pierre has yet to defeat fourth-ranked Jake Ellenberger, fifth-ranked Demian Maia, seventh-ranked Martin Kampmann, eighth-ranked Tarec Saffiedine or ninth-ranked Robbie Lawler.
But what threats could Ellenberger, Maia, Kampmann, Saffiedine, Lawler or even MacDonald—if he ever gets the opportunity—offer to GSP that guys like Nick Diaz, B.J. Penn, Josh Koscheck, Condit and Shields didn't already present?
In other words, if Hendricks cannot end his reign, then the rest of the heap at 170 will likely meet similar fates against St-Pierre. Of course, that's unless GSP beats himself—like he seemingly did in his only two career losses to Serra and Matt Hughes.
"It's a very tough division," St-Pierre said on an episode of The Joe Rogan Experience. "I'm not stressed. I try to take it one fight at a time and focus on one guy at a time. I have no choice. I cannot split myself in half."
Something in the depths of St-Pierre's soul certainly altered after getting embarrassed and demoralized at the hands of a perceived inferior fighter in Serra at UFC 69.
Shortly after UFC 69, GSP linked up with former training partner Firas Zahabi, wisely naming the diabolical Brazilian jiu-jitsu black belt his head trainer before his next bout with Koscheck at UFC 74.
Zahabi not only forced St-Pierre to magnify his intellect in the Octagon, he also helped the 31-year-old Canadian optimize his strength and become the sport's most dynamic and explosive athlete.
A former Canadian Muay Thai champ, Zahabi has aided in St-Pierre's development as the sport's most cerebral game planner, teaching the Renzo Gracie disciple to become the most controlling and dominant welterweight the UFC's ever seen.
St-Pierre also surrounded himself with the proper doctors and teammates when the unthinkable happened to his right knee in 2011.
With support from a cluster of upper-echelon teams, including his allies at Tristar Gym and Jackson's MMA, St-Pierre recovered from an ACL tear that kept him on the shelf between April 2011 and November 2012.
In his return to the Octagon, GSP outshined Condit at UFC 154 in a barn-burner that MMAValor.com deemed the 2012 "Fight of the Year."
GSP most recently used a thorough beating to silence one of his most outspoken critics, former Strikeforce champ Nick Diaz, at UFC 158.
Although he's clearly still in his prime, St-Pierre, who was casted as a villain in the 2014 movie Captain America: The Winter Soldier, could soon depart from the sport he adores, still essentially in his heyday.
"I have goals for my career but I have much bigger goals than this," St-Pierre said to Rogan. "One of my goals is to be married (and) have a wife with at least five kids. Four or five kids, minimum. That's one of my goals. I'm not there yet but that's one of my goals."
Until then, however, fans and experts can only dream about a superfight between St-Pierre, the most efficient and well-rounded scrapper in MMA history, and Silva, the most venomous and unpredictable fighter ever.