In a sport with such a noted history of putting the cart before the horse when it comes to promising young prospects, it's difficult to hold back from proclaiming Errol Spence Jr. as boxing's next great star. 

Spence, 27, the quiet unbeaten welterweight with poise beyond his years, has simply looked that good throughout his steady rise. With flawless technique and an instinctive nature for knowing when to finish opponents, Spence (21-0, 18 KOs) has become the darling of critics. Everyone from legendary HBO commentator Jim Lampley to Floyd Mayweather have shared their prediction that he's the future pound-for-pound king in waiting. 

But Spence, a southpaw and former U.S. Olympian from Desoto, Texas, will need to earn that praise, of course, when he travels to Sheffield, England, on Saturday to challenge Kell Brook (36-1, 25 KOs) for the IBF welterweight title (Showtime, 5:15 p.m. ET). 

Despite the slow yet steady rise Spence has enjoyed of late, slicing through one competent test after another, he simply hasn't faced an opponent on Brook's level. In essence, that's what makes Saturday's fight so good. This isn't the next logical step in Spence's progression as much as its a straight up dive into into the deep end of the pool. On foreign soil, no less. In his opponent's backyard. 

For all of the questions we have about whether Spence is everything we believe or (in some cases) hope he is, as boxing fans constantly flock to the next shiny toy or potential savior, this is the fight constructed entirely around the premise of finding those answers. 

The only opponent Spence has faced who is anywhere close to Brook is former junior welterweight titlist Chris Algieri last April. And if you're looking to use that fight as a litmus test to gauge if Spence is ready for Brook, that's where the hard part comes in. The manner in which Spence surgically destroyed the normally resilient Algieri, forcing him into submission in a way even Manny Pacquiao couldn't, it's hard to stop yourself from going too far and tabbing Spence as the outright favorite on Saturday. 

The best part about this fight, however, is that Spence may prove to be all he's cracked up to be and it still might not be enough to beat Brook. Arguably the top welterweight in the sport, Brook presents almost the perfect prototype of what a top 147-pound fighter should be with his balance of power and speed, and a good mix of technical skill with poise and toughness. 

The fact that Brook, who has long fancied a move toward a more manageable weight cut at 154 pounds, went out of his way to take this fight is something that shouldn't be glossed over. 

Last September, Brook dared to be great by moving up two weight classes to middleweight and challenged unified champion Gennady Golovkin. Brook fared well off the start but was ultimately stopped due to a broken eye socket. 

But keeping his world title at welterweight was important to him, as was taking on the toughest test available in Spence. If it wasn't for that, we wouldn't be seeing this fight on Saturday and wouldn't have had the chance to find out how good Spence really is. 

"I feel like this is a legacy defining fight for me," Spence said during last week's media teleconference. "Most guys with my pedigree get the title handed to them in some type of way. They don't go across seas to fight the hometown guy against a good fighter like Kell Brook. That's really unheard of. So I definitely think I get a lot of credit for going overseas and fighting Kell Brook."

Brook, 31, is unbeaten at 147 pounds and has made three defenses thus far of the title he won in 2014 against Shawn Porter. 

But he admitted he respects Spence's decision to test himself in such a difficult fight. 

"It just shows me that he believes in his abilities," Brook said. "I was in the same position that he was in. End of the day, it's just going to be me and him in the ring no matter where it is. It's just going to be me and him. He believes in his talent and I know he's going to be up for it because when I was coming to fight Porter as the challenger, it was a dream and it's now his dream fighting for the biggest fight of his life, for all the marbles and the world title. 

"I know what he's going through. He's flying over to England, I flew to America. There are many things that go through your mind. You question yourself; you ask yourself many, many questions. I know all that is being asked of him to get him to this stage."

On Saturday night, we'll find out whether Spence, the decorated prospect, is fit to where the crown. In many ways, this is what big-time boxing is all about.