OPINION: They say in heavyweight boxing one punch can change a career.
It wasn't quite one punch for Andy Ruiz, but the Mexican-American caused a sporting boilover on Sunday (NZT), stopping Anthony Joshua to claim heavyweight gold.
Ruiz was a 45-1 underdog with some of the bookies on Las Vegas, but put those predictions to shame with a career-defining performance.
But is it the biggest upset in heavyweight history?
It's certainly in the hunt.
5. Hasim Rahman beats Lennox Lewis via TKO, 2001
Lewis was fresh off the dismantling of David Tua and thought of by most as the greatest heavyweight since Muhammad Ali.
Rahman was an excellent boxer with punching power but had a habit of fading if pushed beyond the middle rounds. Rahman was considered a tune-up fight for Lewis in the build-up to a mega showdown with Mike Tyson.
Rahman entered the fight with a 34-2 record, which included a 1998 TKO loss at the hands of Tua, but most thought the Brit would be too classy for the American.
They were wrong.
Rahman and Lewis took centre stage at altitude in Carnival City, South Africa. The 20-1 underdog stunned a pro-Lewis crowd, dropping the Brit in the fifth round to win the heavyweight championship.
Lewis' first career loss in seven years and just the second of his stellar career provided the greatest moment of Rahman's career, and the hope he was the next great American heavyweight.
However Lewis would gain revenge a few months later, stopping Rahman to reclaim his heavyweight titles.
4. Muhammad Ali defeats George Foreman via knockout,1974
'The Greatest' was only 32 when George Foreman defended the heavyweight championship against him in Zaire in 1974.
But many felt Ali's best days were behind him. Despite a career record of 44-2, Ali had split two competitive fights with Ken Norton and taken a battering in a victory against Joe Frazier in January 1974.
Foreman was Mike Tyson before Mike Tyson was a thing. He was a cross between Tyson and Ali's incredible power, a tremendous physique and undoubted boxing credentials.
Foreman was undefeated in 40 fights and was coming off a second-round demolition of Norton just a few months earlier. Add to that a TKO of Frazier, and Foreman was literally the baddest man on the planet.
But Ali came with a plan. To take a licking, but just keep on ticking. He was able to absorb all of Foreman's offence, holding his hands high in the corner and forcing the younger man to blow his gasket.
And that's exactly what happened. Ali landed a huge blow in the eighth round that staggered Foreman before eventually overwhelming his fellow American and scoring a knockout win.
At the time it was regarded as the biggest upset in heavyweight history.
3. Oliver McCall defeats Lennox Lewis via TKO, 1994
McCall was your classic boxing journeyman. He had gathered some decent wins in 29 fights heading into his opportunity against Lewis.
But he had lost to the likes of Tony Tucker and Mike Hunter along the way. Lewis was undefeated in 25 fights, with 23 stoppages and looked as close to an unbeatable heavyweight as there ever had been.
The stage was set for Lewis, fighting in front of his countryman at London's Wembley Stadium, but it would quickly turn into a bad dream for the entire United Kingdom.
McCall clocked Lewis with a huge right hand in the second round, sending the then WBC champion to the canvas. Lewis got back on his feet but his legs wouldn't cooperate and the referee stopped the fight.
McCall lost the title to Frank Bruno and his career would then unravel, including an in-ring mental breakdown in a rematch with Lewis in 1997.
2. Andy Ruiz Jr defeats Anthony Joshua via TKO, 2019
Let's be honest, Ruiz looks more like a sumo world champion than a boxing world champion, but the man can fight. He has slick boxing skills, a granite chin and a pure fighter's heart that was on show for the world to see against Joshua.
AJ was a huge favourite - he had dispatched the likes of Carlos Takam, Joseph Parker, Dillian Whyte and Wladimir Klitschko in 22 fights.
His power has been compared to Tyson and Foreman of years past, while he also possesses Olympic gold boxing credentials.
Despite Ruiz winning 32 of 33 fights (his only loss was against Parker) there wouldn't have been a single soul inside Madison Square Garden that truly believed he could get the job done.
And it was all going to plan for AJ when he dropped Ruiz in the third round, but two minutes later the Brit had been floored twice himself. Joshua recovered somewhat but in the seventh round Ruiz unleashed a brutal onslaught of punches to drop the champion for a third time.
A short time later, Joshua took knee resulting in a stoppage from the referee.
A huge upset, but not the biggest in heavyweight history.
1. James 'Buster' Douglas defeats Mike Tyson via KO, 1990
We have a winner. As much as Joshua has been considered a modern-day Tyson, Iron Mike looked unflappable through the first 37 fights of his career. There were no signs of weakness, no dodgy chin, no issues with the gas tank and no questions about motivation.
Tyson was literally the scariest human on the planet, with 33 stoppages in 37 fights heading into the showdown with Douglas in Tokyo, Japan. This was considered a bonafide walkover for Tyson with Evander Holyfield awaiting a few months later.
Tyson was a 42-1 favourite but reportedly he had an interesting few days in Tokyo in the lead up to the fight that included all-night benders.
Even then, the thought of Tyson losing was unthinkable. But Douglas was riding a wave of emotion after losing his mother in the weeks leading up to fight, and he did possess a slick jab that Tyson spent the majority of the fight eating.
But late in the eighth round, Tyson landed a huge uppercut on Douglas, sending him to the canvas. The fight looked over.
But Douglas recovered sufficiently, although after the fight, the Tyson camp would complain that the count was slow and that Douglas had taken longer than ten seconds to get back on his feet.
The end of the fight came just 35 seconds into the tenth round.
Douglas unleashed a brutal uppercut, followed by a a four-punch combination of hooks that sent Tyson to the canvas for the first time in his career.
The fight was over and we had the biggest upset in boxing history.