Hasim Rahman Sr. Says He'll Fight Logan, Jake Paul Same Night, KO Both

If Jake Paul can't fight Hasim Rahman Jr. on August 6, there's someone else willing to step in the ring in his place -- Hasim Rahman Sr.!!

That's right ... the 49-year-old, 2x heavyweight champion tells TMZ Sports he's down to fill in for Jr. and box the Problem Child.

Oh, and for good measure, he says he'll fight Logan, too ... same night.

"How about this?" Hasim says, "If somebody would sanction this, I will fight Jake and Logan back to back. We can go eight rounds a piece. Neither one of them will make eight rounds but we can sanction for eight rounds and I promise you, if I don't knock Jake and Logan out, they win."

Of course, Jake and Jr. were set to box Saturday at MSG ... but the fight was scrapped after Paul accused Rahman of ignoring their contractually agreed-upon weight limit.

Now, let's be honest ... two fights in one night ain't happening, but you get Hasim's point. He isn't all that impressed with what he's seen in the ring from the Paul bros.

In 2001, Rahman Sr. shocked the sports world when he knocked out one of the greatest heavyweight boxers ever, champ Lennox Lewis ... becoming the unified heavyweight champion of the world.

Throughout his career, Hasim racked up a 50-9-2 record with 41 KO's. He retired in 2014.

We also asked Rahman about the possibility Jake and his son could still fight another time ... and Hasim had a suggestion for ensuring the terms of the contract are followed.

"If the public demands it, both sides can put up a million dollars in escrow. That way we can be sure that ain't nobody gonna not make weight. If somebody miss weight, whatever the contractual demands are, they will be met or somebody gonna lose their million dollars."

So will it be Hasim Rahman Sr.? Rahman Jr.? Tommy Fury? Someone else? Stay tuned.