"He's handling his business and getting better. I look forward to him being out and back on his feet," Casey told E! News on the sidelines of Toronto International Film Festival.
In August, reports came out that Ben was seeking professional help following what a source described as a "really rough" period of time for him.
MORE PICS: Ben Affleck back to rehab after Jennifer Garner intervenes
Over the weekend, photographers clicked Ben's rumoured girlfriend, Playboy model Shauna Sexton, stopping by the rehab where he is staying.