Former Republican presidential candidate and Donald Trump supporter Ben Carson called on the GOP front-runner to "up his ground game" in a Fox News interview late Thursday.

Carson's advice, he admitted, was a direct contradiction to campaign manager Corey Lewandowski's strategy of "let Trump be Trump" and ignoring outside advisers who would try to change him.

"I think you need the outside people though. There's no question that he's got to up the ground game. He's got to cultivate the delegates and if you don't play that part of the game you're going to lose 100 percent of the time," Carson told host Megyn Kelly.

Carson, who admitted earlier Thursday there are others who would make a better president than Trump, said the Manhattan businessman needs to heed the advice of others and embrace a softer, more presidential tone if he wants to keep winning primaries.

While Trump's rough-around-the-edges facade is part of the reason voters have flocked to him this election, Carson believes he can pick up more supporters by elevating the conversation instead of engaging in party infighting.

"It would be nice if we stopped it [infighting] and if we could be mature. It seems like we can't. I know that we can though. I know we have the intellectual ability to do it and to focus on the things that are important," Carson said.