Cardiff will allow long-serving Kevin McNaughton to leave this summer along with Danny Gabbidon and Nicky Maynard.
Highly-rated Atletico Madrid midfielder Saul Niguez has signed a new five-year contract.
Nottingham Forest have completed the permanent signing of Danny Fox from Southampton.
The left-back spent the last four months of the Championship season on loan at the City Ground, starting 15 games.
Fox agreed a three-year contract at the time of his initial loan deal, and that has now been activated.
The Scotland international will work under new manager Stuart Pearce next season.