Ali, 69, has been battling Parkinson's disease for many years; however, the reason for his stay in a Scottsdale medical center in mid-November was not clear.
"I don't think he stayed very long," John Ramsey, a longtime friend of the former heavyweight boxing champ, told The (Louisville, Ky.) Courier-Journal.
Ramsey, a radio host in Louisville, told the newspaper he spoke to Ali's wife, Lonnie, Thursday night. He said he was told the champ was "home and well."
"He may not be going in the direction you or I like, but no one is on alert," Ramsey said.