Floyd Mayweather vs. Manny Pacquiao II Is No Nostalgia Act, Says Promoter Jas Mathur

If you thought the first showdown between Floyd Mayweather Jr. and Manny Pacquiao was massive … buckle up!!!

Jas Mathur -- CEO of Pacquiao’s promotion company and one of the key figures behind the rematch -- tells TMZ Sports the September 19 clash at Sphere in Las Vegas isn’t just big … it’s historic.

“I’d say huge is an understatement,” Mathur told us, pointing to the original fight’s eye-popping $600 million haul. “You’re talking about a spectacle.”

And this time, it’s not just boxing -- it’s a full sports-entertainment takeover inside one of the most high-tech venues on the planet … with Mathur promising a production that’ll leave fans not believing what they see.

As for the boxers themselves ... don’t expect a nostalgia act after their 2015 bout dubbed the “Fight of the Century.”

“Floyd’s Floyd. Don’t get it twisted,” Mathur said. “50-0 … he does this in his sleep.”

Pacquiao’s no slouch, either ... and according to Mathur, both legends are somehow aging in reverse.

“These two age backwards,” he said. “They’re both on their A-game.”

Of course, not everyone’s sold. Dana White and others have raised eyebrows about the event -- especially the price tag. But Mathur isn’t sweating it, saying this isn’t some back-of-the-napkin idea.

“Everyone has words,” he said. “Why wouldn’t it be expensive? Look at the names we have.”

And he didn’t stop there ... taking a not-so-subtle jab at the UFC boss, questioning fighter pay and even calling out the promotion’s handling of stars like Jon Jones and Conor McGregor.

But when fight night hits Vegas?

“Break records, set new heights, set new standards,” Mathur said. “They did it once … they’re gonna raise the bar all over again.”