Adrien Broner Wants Nate Diaz on Floyd, Conor Undercard

Adrien Broner just called out a BIG name for the Floyd Mayweather vs. Conor McGregor undercard ... telling TMZ Sports he wants to fight UFC badass Nate Diaz.

There's just one minor issue ... Broner is taking on undefeated Mikey Garcia in a big Showtime boxing event on July 29 at Barclay's Center -- one month before MayMac. But AB has a plan.

"If I come out unmarked ... like I usually do, I’ll be willing to fight on Floyd’s undercard," Broner said. "If we can make it happen, let’s do it."

Might sound crazy -- but remember, Broner is Floyd's boy -- they're super tight -- and Team Mayweather has complete control when it comes to booking the undercard. Don't completely rule it out.

No response yet from Diaz ... who has been chillin' since his rematch with Conor in August.

And get this ... Broner also explains why he thinks McGregor has a REAL SHOT at beating Floyd.