When Anthony Joshua and Wladimir Klitschko face off in front of a record-breaking 90,000 fans at Wembley Saturday, there will be a difference of 50 fights and 314 rounds between them.
Now 41, with many claiming his best years are behind him, Klitschko has a wealth of experience on his side to combat Joshua's young legs and explosive power.
Ukrainian Klitschko has, at one time or another throughout a glittering 21 year career, held the WBA, IBF, WBO and IBO heavyweight titles.
Up until his shock defeat to Tyson Fury 18 months ago, the Ukrainian was undefeated for over a decade -- a run dubbed the "Klitschko era" due to his and older brother Vitali's dominance of the heavyweight division.
The 27-year-old Joshua, on the other hand, has not only endured just a quarter of the professional fights Klitschko has, he's barely even had to absorb a punch.
Dillian Whyte's powerful left hook, which made Joshua's legs wobble all over the ring during their British heavyweight title bout in 2015, is the only real test of his otherwise untried chin.
The age gap between the fighters is such that Klitschko has been boxing for the same amount of time Joshua has been alive.
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The 27-year-old Briton goes into the fight defending his IBF title, while also trying to win the WBA and IBO titles vacated by Fury after he tested positive for cocaine
"I don't hate Klitschko, I don't dislike him, but I want to beat him," Joshua told hoards of adoring fans after tipping the scales at 250.1 lbs at Friday's weigh in.
It's the heaviest Joshua has been during his short but, so far, straightforward career.
"I've never seen Anthony this big. He looks like Arnold Schwarzenegger in his body building prime," Klitschko marveled during the open workouts earlier this week.
The Ukrainian, meanwhile, weighed in at 240.6 lbs -- half a stone lighter than his usual fighting weight.
"You never know how the fight will go," Joshua responded when asked if this bout is his hardest test to date.
"This could be an easy fight, or I could go out there and something could happen and then maybe a fight that wasn't supposed to be so hard could become harder.
"All I have to do is make this fight as easy as possible and win in good fashion."
Known for his analytical approach and strategic fighting, Klitschko finds himself in the unusual position of being a challenger once again.
"Is it a degradation that I'm a challenger and an underdog in this fight? I don't think so. I think it's a great opportunity," he insisted.
"I feel young, hungry, humble and totally obsessed with my goal to raise my hands again as the winner of this fight."
At Thursday's pre-fight press conference, the biggest talking point came when Klitschko pulled a USB stick out of his pocket.
He claimed, with unnerving confidence, that he had recorded his prediction for the outcome of the fight.
The only person who will be able to watch the video, he said, is the highest bidder, with all proceeds going to the Klitschko Foundation, drawing warm applause from the crowd.
"It's strategy, isn't it?" Joshua said. "I'm just focusing on the fight. I'm not downloading no USB, bringing that to press conferences.
"I didn't really take it the way he was hoping. It was an attempt at mind games."
Klitschko's trainer, Johnathon Banks, has said that defeat would render his career meaningless, while Joshua previously claimed victory would make him an "overnight legend."
Whatever happens, Saturday night will live long in the memory.