Now, Riley has admitted that those issues revolved around substance abuse.
"He did have a significant performance-based anxiety out there under the spotlight," attorney Shingles says. "And he turned to drugs to self-medicate. That trended into abuse."
Shingles claims that his client informed The Voice of his substance abuse problem and the show sent Riley "on their own dime" to a Pennsylvania rehabilitation facility. He apparently remained there for 14 days, after which Shingles says Riley received a certificate of completion.
"He went back for the premiere," Shingles says. Riley performed at a Voice premiere party in West Virginia on February 24. "Thereafter, he left the show."
NBC has no comment. However, a rep noted that the premiere episode was filmed far in advance of its actual release.
Shingles also maintains that Riley was not fired from the show, as former assistant Christopher Mapp claims.
"They were respecting Anthony's privacy, which was nice," he says.
Previously, Riley released a statement to Steubenville, Ohio's WTOV9 that touted the earlier "medical issues" explanation:
"Unfortunately, I will be unable to continue my journey on 'The Voice' for season 8 due to medical reasons. Any other rumors are just that."
Riley will perform Saturday night in the Ohio Valley, where Shingles says he has "some sober support."
*An earlier version of this post indicated Riley returned to Los Angeles for a Voice premiere. That is incorrect. Chris Mapp noted that Riley performed at a Voice premiere in West Virginia following his stay in rehab. The change has been reflected above.