Terence Crawford, Errol Spence Say Win Makes Them Best Boxer In The World

Errol Spence and Terence Crawford have a lot more than their undefeated records and four shiny belts on the line in Vegas Saturday night ... both superstars agree, the winner is the best boxer of this generation!

TMZ Sports is on the ground in Sin City ... and we talked to both fighters just days before the biggest clash of their professional lives.

"I can't wait to show everybody why I am not the best 147-pounder in the world, but the best fighter, period," 33-year-old Spence said.

If you're a boxing fan you can hardly wait. It's the scrap you've wanted for years, but believed would never actually happen -- two undefeated greats, champions -- battling in front of the world ... 28-0 (22 KO) Spence vs. 39-0 (30 KO) Crawford.

But, it is going down ... and it's only a day away.

"It took a while for me and Terence to happen, but it's happening at a great moment right now," Spence told us.

"We're fighting for all the marbles. He's undefeated, I'm undefeated. I think it's gonna be a great fight, a great showing, and we're definitely gonna give the people their money's worth on Showtime Pay-Per-View."

Crawford also believes the winner will rightfully lay claim to being called the best active boxer alive.

"I wouldn't say the greatest fighter of all-time, I would just say the greatest fighter of this era," Bud told us.

As for the motivation to take such a risky fight ... both men acknowledge they're going home with a big ol' check, but it's not all about the money. Not even close.

"I'm more motivated about beating him because it's a huge rivalry between us. Everybody always attaches our two names together for probably about 6 or 7 years now," Errol told us.

"It's more of a competition factor more than anything. I want to defeat him. I find gratification in defeating him more than anything else."

Despite being at the center of the storm, the magnitude of the fight isn't lost on Terence, either.

"I definitely believe [it's the biggest fight in a long time]. This is the fight that everybody been wanting. You have the two of the greatest fighters of this era going head to head with each other, and it's gonna be a great night of boxing Saturday night."

As if the main event wasn't enough, the card also features several other kickass fights, including the great Nonito Donaire -- a future Hall of Famer -- taking on Mexican contender Alexandro Santiago for the WBC Bantamweight World Championship. Isaac Cruz is also fighting undefeated Giovanni Cabrera.