Speaking to the CT, Chris Coleman said: "Marcus has been a great servant to this club and a terrific pro who is well respected. "We all think a lot of him but we think it is best because we want to make a change and it will probably be best for Marcus as well to have a fresh start.
"It was a tough decision and it wasn't news I wanted to give him because he is a really nice lad and I have enjoyed working with him.
"He's 34 and had a tough year but he has got a couple of years left in him yet, but for us we have got young Chris Hussey coming through, Jordan Clarke, Jermaine Grandison and there is also Martin Cranie, Stephen Wright, James McPake, Richard Wood, and hopefully Leon Barnett, so we feel we have got enough defenders and that's where Marcus has lost out."