Barclay was a potentially solid lineman in the beginning. It was those injuries that stole it all from him. Each one saps a little more away from a guy, and in the end, it's just too many injuries, and not enough time being able to becoming better, and on the field.
I feel bad about him leaving, but a guy has to be pretty good to invest cap space in a guy who can't be counted on to at least take the field as a back-up.