Floyd vs. Manny Rematch: 'More Likely Than Not' ... Says Bob Arum

Manny Pacquiao's promoter tells TMZ Sports a rematch with Floyd Mayweather is "more likely than not" ... but says there are still some serious obstacles to overcome.

We spoke with Bob Arum who says, "It's close to 50/50 but probably leaning more toward the fight happening ... more likely than not."

Arum says he hasn't spoken with Manny or Floyd specifically about the rematch -- but says, "If the match was available, I believe [Manny] would come back for that match."

Arum also says he knows Showtime has serious interest in Mayweather vs. Pacquiao II -- and that's an important component to making the fight happen.

So, what are the obstacles? For starters, both guys claim they're retired ... with Manny focusing on a senate run in the Philippines and Floyd focusing on promoting his fighters.

But Arum says, "If either man agrees to fight, my feeling is that they won't be able to resist."