The former Dundee United right-back has been beset by injuries since his move to his boyhood heroes in January 2006.
After talks with Parkhead boss Tony Mowbray, he may join several fringe players in the Celtic squad who could leave the club when the transfer window opens.
"Obviously, I love the club and first and foremost I would like to stay for years but at the end of the day I'm not playing and it looks like I have to look elsewhere," he said.
"I'm 25 now and at the stage of my career where I want to be playing.
"I have missed a lot of games through injury and, now that I'm fit, it's frustrating to find myself frozen out of the team.
"And because of the under-21 rule, I'm not even getting on the bench, so on a match day I'm in the house and that's not really where I want to be.
"You know the manager, he is perfectly honest.
"He doesn't mess you about and I think he has made it clear to a lot of players that he wouldn't stand in their way if something came up.
"He gives you encouragement but he has said that Andreas has the shirt and that's that and I need to accept that.
"But, as I say, it's difficult come a match day when you are not involved.
"I could still be here. The best situation is that I'm in the team and playing well but that looks a bit far off now.
"I will need to keep working away and see what happens come January."