Keith Thurman Rips Floyd Mayweather, You Ducked Me and You Know It!

Keith Thurman says Floyd Mayweather is straight CHICKEN -- accusing the boxing legend of running scared before he retired and now he's calling Floyd out.

"If he wanted a real fight, he would have saw me years ago," Thurman tells TMZ Sports.

"You never wanted to fight me. I was right there right underneath you for years. I was the #1 contender of the WBA and then they made you super champion so that our names didn't have to be in the same sentence together."

FYI, a WBA Super Champ is a fighter who holds multiple titles in the same division -- and is exempt from mandatory title defenses. Essentially, Super Champs can pick their own opponents.

Thurman says during Floyd's active fighting days, there were plenty of opportunities to make a fight between the two ... but Mayweather wussed out and didn't want the smoke.

Now, Thurman -- who's 29-0 -- is gearing up for the biggest fight of his career against Manny Pacquiao on Saturday ... and he knows a victory could open some huge doors.

In fact, Keith says he sees big fights with stars like Terence "Bud" Crawford and Errol Spence in 2020 ... and says, "I'm very open to those contracts."

But, for now, Thurman says the plan is to beat Manny and then take the rest of 2019 off to gear up for a massive 2020.