Herschel Walker -- Donald Trump Is a Man of His Word ... I Should Know

Donald Trump's campaign has a new, powerful ally -- football legend Herschel Walker is backing his ex-boss because of two words -- unpolished and trustworthy.

Walker knows The Donald well ... he was a contestant on "Celebrity Apprentice" and toted the rock for the New Jersey Generals -- Trump's USFL team -- back in the '80s.

He tells TMZ Sports he has no issues with Trump's incendiary straight talk because ..."I'm tired of politicians. I'm tired of promises. I know Donald will keep his word. He'll do what he says."

As for Trump's more controversial remarks -- Megyn Kelly and Mexicans -- Herschel thinks he does need to clarify a few things, but adds, "I guarantee his plan is not to deport everyone. If you're good, there will be a path to citizenship."

Walker adds, "He's not a polished politician and I hope he doesn't become one."

For now, he's stopping short of pledging his vote to Trump -- he's got an eye on Ben Carson, too -- but he's buying in to Donald's slogan, "Make America Great Again."