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.
Paul Pogba's agent has again stressed that the young Frenchman is yet to decide whether to join Juventus or not.
The Manchester United midfielder is out-of-contract in the summer and the young Frenchman has thus far refused to pen a new deal at Old Trafford.
Juventus have been tracking for a number of months and deal is on the table for him in Turin, and fresh reports in Italy had claimed he had finally opted for the Old Lady.
However, Mino Raiola says Pogba is yet to decide on United or Juve.
"Paul has not agreed any move yet. He has a straight choice between United and Juventus but I think he will make his mind up soon," Raiola told TalkSport.