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.
Former Scotland striker Dougie Freedman has criticised the Scottish Football Association for not giving Craig Levein the time designated in his contract.
Levein was sacked as Scotland manager on Monday with 20 months remaining on his four-and-a-half year contract, which the SFA say they will continue to honour, although Levein is seeking legal advice.
Levein won just three of 12 competitive matches in charge and the SFA board acted to "relieve him of his duties" with Scotland bottom of their World Cup qualifying group with two points from four matches.
The board has been streamlined since Levein was appointed in December 2009, with Stewart Regan and Campbell Ogilvie since replacing Gordon Smith and George Peat as the leading decision-makers.
But Freedman believes the governing body were morally obliged to allow Levein his full term.
Freedman, speaking as he was introduced as Bolton manager after leaving Crystal Palace, said: "I think it's very sad what's happened to Craig Levein.
"I think it's very disappointing that the media have gone after someone that's not been given enough time.
"I believe at national level, if you sign a four-year contract then you're obliged to stay for four years and at the end of the four years you can assess it then.
"Why don't we look at the people who gave him a job - did they pick the right manager at the beginning?
"I'm disappointed for Craig and I'm disappointed with the results, but I don't like the decision to sack someone when they've signed a four-year contract.
"Let's have a look at the people who gave him the job first."
The SFA will formally launch their recruitment process after next week's friendly against Luxembourg.
Caretaker manager Billy Stark, bookmakers' favourite Gordon Strachan, former Scotland striker Joe Jordan and Freedman's predecessor at Bolton, Owen Coyle, have all declared themselves open to offers, while the likes of Alex McLeish and Stuart McCall have ruled themselves out.
Freedman, who scored against Latvia in one of his two Scotland appearances, added: "Looking forward we are in need of some stability. I think we've got good players. I see some names bandied around.
"I don't know who I'd pick but I think the next man, whoever's in that job, should be given a two or three-year campaign to get it right."