Paul -- whose rematch against KSI was one of the most-watched events on DAZN in 2019 -- had appeared on Barstool's KFC Radio in December and initially called out AB.

"Antonio Brown, I wanna f**k you up," Paul said at the time.

LP essentially explained that AB is out of a job and loves the spotlight -- and it could actually be a huge event.

Well, Brown is down ... tweeting at Paul late Monday night, "Square up!"

Paul fired back, "I’d drop you faster than the patriots."

Things have escalated to the point where a betting site has released betting odds on the possible matchup ... with Logan being the overwhelming favorite. AB could barely believe it.

So, how would they measure up?

Logan Paul -- 24 years old, 6'2", 190 lbs.

Antonio Brown -- 31 years old, 5'10", 185 lbs.

IT'S NOT OUT OF THE QUESTION!!!

Plus, Logan's right ... Brown's unemployed, a freak athlete and loves attention.

Logan has two fights under his belt -- though the first bout with KSI wasn't officially sanctioned. He lost the rematch but people were super impressed with his fighting skill.

Paul has been training ever since and has said he's seriously interested in taking more fights in both boxing and MMA.

As for Brown ... he's been unemployed since the Patriots cut him early in the 2019 NFL season and there's been so much off-the-field drama with him, no one really knows if another NFL team will ever take a chance on the WR ever again.