Anthony Joshua has admitted that "a fear of losing" drives him on as the British star weighed in almost a stone lighter than his last outing, and his leanest for four years, in advance of this super-fight with Joseph Parker here at the Principality Stadium.
The unbeaten 28 year-old will take a huge step towards unifying the heavyweight division if he adds Parker's WBO title to his own IBF and WBA belts in the Welsh capital. The phoney war is over.
Joshua has promised an improved performance on his last outing against Carlos Takam and when he tipped the scales at 17st 4lbs it was clear how he intends to deliver on that vow: the Londoner aims to be sharper, faster and more dynamic than his New Zealand opponent.
But while the performance is important Joshua knows it is simply critical that he end the fight with arms aloft, his professional record improved to 21 wins from as many bouts.
Joshua walks a tightrope of expectation every time he steps into the ring and the pressure is on the heavy favourite to deliver a victory that ensures his blossoming career and commercial appeal - and his sponsors have been obvious here - continue their frighteningly meteoric rise with the bid to conquest the US market next on his horizon. He dare not fail.
"There's definitely a fear of losing because it keeps me going," explained Joshua. "I have to make sure I stay focused on the task at hand. The fear of losing keeps me motivated because I know how quickly the tables can turn. One minute you're the man and the next you're not. I know how easy it is to be forgotten about."
Concerns remain, though, that he is a "work in progress", as assessed by trainer Rob McCracken. Yet the hype around the 'AJ' juggernaut thunders on. It is eleven months since he climbed off the canvas to knock out Wladimir Klitschko in the fight of the decade in front of 90,000 at Wembley Stadium. It is five months since that somewhat flat display against Takam witnessed by 78,000 here at the Principality Stadium. They were contrasting evenings that gave the young fighter great experience but also raised questions - not least from himself - that are yet to be answered.
His physique shows his dedication to the task, McCracken disclosing to Telegraph Sport that Joshua has been "more relentless and ruthless than ever in training."
On Saturday night that must transfer to the ring. Parker is a fellow unbeaten world champion, and the 26 year-old is himself six pounds lighter than his last title defence, against Hughie Fury in Manchester. The ice-cold Parker is adamant he is "prepared to go to dark places" to make his own mark on the history of the sport and with the biggest ever boxing audience in New Zealand expected to tune in - an estimated half a million fans - he faces his own pressures.
And while the hype is over this fight is big. Very big. It will be aired in 215 territories globally, compared to 140 countries that showed the Joshua-Klitschko bout. As with that fight the build-up to this occasion has been respectful, the two men swapping handshakes rather than insults.
It is not a foregone conclusion, either. Glenn McCrory, the former world cruiserweight champion and a fighter brave enough to have sparred over 90 rounds with 'Iron' Mike Tyson, told Telegraph Sport that he believed Parker must "adopt an Evander Holyfield-like strategy" if he is to return home with the two belts. That means taking Parker "must take Joshua into the late rounds, move and box smart, and make raids" on the two-belt champion, from the outside.
"It has to be like Holyfield when he fought Riddick Bowe the second time," fight commentator McCrory told me. "Be fast, dynamic, slip jabs, make the bigger man work... match him, be faster."
Those who favour Joshua - and that is to say the vast majority - do so because of his imposing physicality, the experience gained in those two ground-breaking stadium fights. By going through 21 rounds and pulling through when in deep trouble against Klitschko, Joshua has shown the world he has heart, chin and stamina. He is a champion, despite being a work in progress.
What we do not yet know is how Parker will respond under that kind of pressure. He has never been badly hurt in a fight, never been down. We have not yet seen him come through a tunnel of trouble, raise himself from the duress of being hurt, nor indeed will he have experienced an occasion or atmosphere such as that he will encounter when he makes his ring walk tonight. His team insist he is ice cool, but will the cauldron of Cardiff have some effect - either positive or negative?
"The first few rounds can got several ways," explained Parker. "We can either test each other out, or we can go in for the kill. It just depends on who is going to follow the game-plan first, and who is going to execute it to the best of their ability. People betting on Joshua to knock me out are making a big mistake. Everyone will be in for a big surprise. I back my ability and I have a great chin."
Against that, Joshua believes he has had "the best camp of his career" and is confident he can finish his rival.
"I want this to be a complete performance. If I had a bet, I would put it on Anthony Joshua to knock Joseph Parker out," said the home fighter. "Losing that little bit of weight has made things easier. I'll be a little bit sharper and able to react a little bit quicker."
On the undercard, Alexander Povetin, the WBA heavyweight No 1, meets another Briton, David Price, who has a last chance saloon opportunity, but the Russian Pagan - who has tested positive for meldonium in the past - should emerge victorious and is the likely next opponent for Joshua, at Wembley Stadium, in the summer.
So far, everything has gone to plan for Joshua. But there is no way that Parker can be written off. He may be shorter, lighter, and a long underdog. But he is young, fast, undefeated, ambitious and very tough.
Parker will give his all, and make it a great spectacle, but there is just the feeling that Joshua's physicality may tell from five rounds onwards, and he should take over in the fight. There is so much on the line for both men, on an occasion for the sport to savour. Fight nights do not get much bigger than this.
All you need to know
The schedule
•The undercard live Sunday 5am, Sky Channel 65
•Parker v Joshua live Sunday not before 8.30am, Sky Channel 65.
Here's the full schedule for the undercard before the main event. •Alexander Povetkin v David Price (WBA and WBO heavyweight intercontinental and international). •Ryan Burnett v Yonfrez Parejo (WBA bantamweight). •Anthony Crolla v Edson Ramirez (lightweight). •Joe Cordina v Hakim Ben Ali (vacant WBA lightweight). •Josh Kelly v Carlos Molina (vacant WBA international welterweight). •Morgan Jones v New Zealander Mose Auimatagi Jr (super middleweight). •Sean McGoldrick v TBA. •Joshua Buatsi v TBA.
The fight
Parker v Joshua will not be before 8.30am and is expected to start around 10am.
Daylight saving ends at 3am tonight so remember to turn your clocks back one hour.
Anthony Joshua Born: Watford. Age: 28. Height: 198cm. Reach: 208cm. Weight: 113kg. Total fights: 20. Wins: 20. Wins by KO: 20.
The Herald will also be hosting a live blog of the fight from 6.30am.
Going out
Prefer to watch the fight at a restaurant or bar? Here are a few options:
Auckland •Sweat Shop Brew Kitchen will screen the fight along with guest speakers and unlimited breakfast for $50. •The Paddington Parnell will screen the action from 6am with an entry fee of $15, and optional buffet breakfast for an additional $10. •The Kingslander will be open from 6.30am, offering a $20 package that includes entry, a buffet breakfast and raffle tickets. •The Fox Sporting Bar & Restaurant has an entry fee of $20; doors open at 6am.
Wellington •The Cambridge Hotel, Realm Bar & Bistro, and Tote Bar & Furnace Restaurant will all screen the fight from 8am with a general admission fee of $19. Ticket sales include a cooked breakfast and beverage.