Luke Oliver has left City after agreeing to cancel his contract early.
The decision allows the big defender to become a free agent - and he is expected to link up with Conference side Forest Green.
The popular Oliver, 29, first joined City on loan from Wycombe in March 2010 under Peter Taylor. After a difficult start, he won over the supporters to such an extent that he swept the board at the player of the year awards in 2012.
But he suffered a shattering blow the following October, rupturing an Achilles tendon which ruled him out for the rest of the campaign - missing both of City's trips to Wembley.
He returned in time for pre-season but has made just four appearances since the club were promoted. He played 119 games in total, scoring three goals.