Amid a rash of shock results in the ring, it would unquestionably top the lot if Saul 'Canelo' Alvarez were to lose against Caleb Plant on Saturday night.
Yordenis Ugas and Oleksandr Usyk were big underdogs before they scotched victory hopes for Manny Pacquiao and Anthony Joshua, respectively.
But neither was quite the outsider with the bookmakers that undefeated Plant has been made for this Las Vegas showdown, when a first four-belt unification of the super middleweight belts goes on the line.
Mexican superstar Canelo (56-1-2) is boxing's pound-for-pound number one and the holder of the WBA, WBC and WBO titles in the division.
Standing in his way at the MGM Grand will be IBF champion Plant (21-0), a 29-year-old from Tennessee who goes by the nickname 'Sweethands'. Canelo is an overwhelming, practically unbackable, odds-on favourite.
A news conference featuring the fighters in September saw the pair involved in a physical altercation, but that will be tame compared to the battle that lies ahead, with Plant adamant he can be the latest to upend a massive favourite.
Plant said this week: "I've dedicated my life to this sport. We're happy to be here, but we're not happy just to be here; we're here to win those belts and become the first undisputed super middleweight of all time.
"I think he knows he's got someone in front of him who's not just here to hand his belt over, not just here to pick up a cheque, but is here to get those belts. That's exactly what I'm here to do.
"I've been the underdog ... maybe this is the third time in my career. It's a place I like to be. But fighting for the first undisputed super middleweight championship of the world, you don't need much more than that. I'm focused, I'm locked in, I'm ready, I'm relaxed and I'm calm. The way I see this fight turning out is [ring announcer] Jimmy Lennon saying, '..and the new undisputed and still undefeated...'."
When it comes to the odds, and all the pre-fight talk, Plant is unmoved by the favouring of Canelo to get the job done.
"People are gonna say what they're gonna say, but they don't get the end say, and I get the end say," Plant said. "I can't focus on what other people have to say about me or what they say I can accomplish. If I had listened to them to begin with, I wouldn't even be here.
"I'm focused on the game-plan and focused on what I've got to do. What people say or odds makers... that has nothing to do with me and that's none of my business.
"By any means necessary, I've gotten here. I've had chances to bow out or step away and to say, 'I'm done, I've had enough', and I haven't, so for Saturday night I just can't wait for the bell to ring. This is history and you're looking at him and his name is Caleb Plant."
When it comes to showtime, Canelo will take some stopping, however.
"We have come a long way to make this happen, and we are just days away from making history," Canelo said.
Canelo was too strong for Billy Joe Saunders when he fought the British fighter in Arlington, Texas in May, leaving his opponent with a broken eye socket and cheekbone broken in three places. Saunders retired after the eighth round of that tussle, handing over the WBO strap.
Plant has not fought since defeating Caleb Truax on points in January. He took that fight 120-108 on all three scorecards, winning every round. His target after the fight was the winner of Canelo versus Saunders, and now that fight is here.
TALE OF THE TAPE
Height: 5ft 8 (173cm)
Reach: 70.5 ins
Professional record: 56-1-2 (38 KOs)
Major career titles: Reigning WBA, WBC and WBO champion
Height: 6ft 1ins (185cm)
Reach: 74 ins
Professional record: 21-0 (12 KOs)
Major career titles: Holder of IBF belt