Ferry and Sullivan leave Pompey
Simon Ferry and John Sullivan have both left Portsmouth Football Club by mutual consent.
Blues boss Andy Awford said: “Unfortunately, Simon and his family have not been able to settle in the south and for personal reasons he has decided to move back up north.
“Hopefully he will be able to return to full fitness and go on to have a successful career.
“It was a mutual agreement with both players and we wish them well for the future.”
Midfielder Ferry scored once 22 appearances for Pompey last season after arriving from Swindon in the summer.
Goalkeeper Sullivan played seven times after joining the Blues in May 2013 and also had a spell on loan at Cambridge.