26-year-old Stevenson, 20-0 (10 KOs), joined Babcock on the "TMZ Sports" TV show (airs weekdays on FS1) ... when the convo turned to 24-year-old Haney's future plans after the undefeated fighter recently announced he's moving up a weight class.

"It ain't really a hope, it's 'I dare him,' like I dare him to come back to 135 [lbs.] and try me. Like I pray that that's what he plans on doing and I can show the world I'm the truth," Shakur said.

"Right now, we're looking at [Vasyl] Lomachenko, but after everything unfolds and he fights Regis [Prograis] and I fight Lomachenko and they can build and make that a big fight, I dare him to come down to 135. I dare him!"

Of course, the fighters, who evolved from phenoms to bonafide stars, have been on a collision course for years ... and even exchanged words in the ring back in May after Devin scored a controversial decision win against Lomachenko.

For the time being, Haney is on his way up to the 140 lb. weight class ... despite the Stevenson fight being there for the taking. We asked Shakur why Devin wouldn't want the opportunity to prove he's a superior fighter.

"I don't know. I'm here but I think as far as for him to come back down and fight me is dangerous," Shakur told us.

"It's a dangerous thing to do. I think that's maybe the reason, I'm a big risk. I'm hard to deal with for anybody and I think he knows that. He's been around me for years so it's hard to deny the fact that I'm a big risk."

We followed up ... asking Shakur if he believes Devin doubts he would win the fight.

"Yes! Yes! I think he believes in himself, but I think when it comes down to me, he knows deep down inside, he knows that I'm the truth."

Then, in his heart of hearts, does Stevenson believe the fans will get the fight they want? Shakur isn't very optimistic.

"If I'm being honest, I'd say 20% [chance the fight happens]."

Shakur continued ... "The logic that they're putting out there is [Devin's] gonna go up for this one fight and then come right back down and fight me for the belts but, like, I just don't see him being that bold. I don't think he got that in him, so I'd say 20% chance."