Ferry spent three years as Duncan's teammate when the two played for the Spurs in the early 2000s.
Speaking on San Antonio sports radio ESPN 1250, Duncan said Ferry is "a jokester."
"He took it obviously too far, but he's not what everyone is calling him. I don't think he's a racist in any way. He said something that was absolutely wrong, but he's not a racist."
Ferry is on an indefinite leave of absence from the Hawks after the public revelation that he recounted a racist remark about Heat forward Luol Deng during a conference call with his ownership group this summer.
Ferry has apologized for his remark.
- Molly Geary