Matt Damon "will always be there" for Ben Affleck.
The 'Good Will Hunting' star is focused on helping his friend through his addiction as Ben admitted himself to rehab to get help with his problems.
A source told People magazine: "He has and will always be there for Ben. They have been friends for years. Let's remember that they each have their own families and careers to deal with."
Meanwhile, Ben's decision to go to rehab is a "major step in the right direction".
An insider said: "One of the key elements with taking control of your addiction is knowing when to seek help, which he did, and it is a major step in the right direction. One crucial aspect of Ben's recovery is for him to be able to seek help when he feels as though he is not in control - when his ongoing treatment and meetings with sober coaches aren't quite enough. The best case scenario is for him to seek help, which he has done willingly, and for that, we are all very grateful and hopeful.
"Addiction is not something that goes away. Every day is a battle for recovering addicts, they are fighting for their sobriety and to lead healthy, balanced lives every day. Ben has been working incredibly hard for the last year to follow a streamlined program designed for him and his journey. He has been attending countless meetings, has continued to work with sober coaches and does his best to follow through with the things that will help him maintain his health."