Well, he's human after all. At the end of a showcase that was originally intended to culminate in his finest hour, Conor McGregor lay prone, gasping for air and contemplating a first defeat in almost six years.
Under no circumstances was the uncouth Nate Diaz supposed to shatter the veneer of invincibility the Dubliner had conjured over the course of a seven fight winning streak at the zenith of MMA but, when all was said and done at UFC 196, that's precisely what he'd done.
With a little over 90 seconds remaining in the second round, the Californian, having shipped every shot in McGregor's extensive repertoire, locked in an air-tight rear naked choke and forced the sport's biggest star to tap in submission.
The travelling Irish hordes that descended upon the MGM Grand Arena to witness the next conquest of their favourite fighting son's tilt for unprecedented domination were jarred into a stunned silence, but no-one looked more incredulous than McGregor.
Remember, he had originally been matched with lightweight champion Rafael Dos Anjos, and was on the verge of becoming the first fighter in history to concurrently hold to two titles.
Following Dos Anjos' omission with a broken foot, Diaz had been drafted in to fill the void, but he had designs on more than just playing the role of a sacrificial lamb.
However, that certainly seemed the case in the early goings of a contest that played out at a breakneck speed.
Untethered by the onerous weight cut that accompanies making the featherweight limit of 145 lbs, McGregor, as he predicted, came of the blocks with a measured ferocity.
Finding his range against the gangly Diaz took longer than usual but, once he did, McGregor uncorked a series of pinpoint combinations which opened a nasty gash over the American's right brow.
The Crumlin native gleefully goaded his foe with every punch that found its target, but Diaz kept coming back for more. As the buzzer sounded at end of the opening stanza, McGregor strutted to his corner, while the blood soaked Diaz looked a dead man waking.
When the action resumed so did McGregor's dominance but only fleetingly. Diaz wobbled him with cracking left hand and quickly went to work. Another straight left rattled McGregor's skull and, in desperation, he tried to take Diaz to the mat.
A grappling savant, Diaz mounted McGregor before taking his back, and then ruthlessly applied the decisive choke.
McGregor was refreshingly magnanimous in defeat, though this slip will be celebrated by many on both sides of the Atlantic, such is his polarizing bombast. Those detractors may shudder at the realisation that he was the first UFC fighter to receive a basic purse of seven figures.
All is not lost either. He's still the featherweight champion and his immediate future now lays in that division. The 27-year-old will almost certainly defend his crown at UFC 200 on July 9 against either Jose Aldo or Frankie Edgar.