Sylvester Stallone -- I'm Not Putting Manny Pacquiao In 'Expendables 4'

More heartbreaking news for the Philippines ... Manny Pacquiao is OUT of "Expendables 4."

In fact, Sylvester Stallone tells TMZ Sports he was never really IN in the first place.

Rumors have been circulating for months that Pacman would make an appearance in the flick -- which isn't really a stretch considering Sly put other fighters like Victor Ortiz, Randy Couture and Ronda Rousey in "Expendables 3."

Plus, Manny and Sylvester are pals ... and Sly didn't really deny it when we asked him about the movie last month.

But Stallone finally put the rumors to bed Tuesday in Beverly Hills ... explaining why Manny's a no-go ... but guys like Arnold Schwarzenegger will probably get the nod instead.

Sorry Manny.