The Backstreet Boys singer said that his bandmate McLean - who entered treatment for "personal reasons" earlier this month - is "doing very well" at the facility and is nearly ready to be released, reports WENN.
"He's good... Just talked to him last night... He's got one more week, he's been there three weeks," Littrell said.
"He's doing very, very well. Sounded very excited... He's working on bettering himself so he can better all of us."
Littrell previously praised McLean for seeking help.