If we sell him, he will definitely come back to bite us on the bum should Wrexham get promoted. In the brief highlights he was mentioned several times in the thick of things. I believe we should keep him as I believe Green is possibly one more injury from retirement. However, if the reports about Walker are true about him losing interest in football, then this doesn't bode well for future setbacks in his career.
Another factor to consider is the possible departure of a few players. It would be better to have personnel ready for a seamless handover, either in the new year or next season