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.
Chelsea new-boy Marko Marin believes the London club is "the perfect fit" for him and hopes the man who recruited him, Roberto Di Matteo, is still the man in charge when he arrives.
The 23-year-old Germany international has agreed to move to the Champions League finalists this summer from Werder Bremen, although there remains uncertainty over who his boss will be, with Di Matteo currently working as manager on an interim basis until the end of the season.
Marin told German football magazine Kicker: "It fits perfectly for me, otherwise I would not have sought this move. Above all, Chelsea's play is based a lot on wide men.
"I had good talks with Di Matteo and I hope he stays."
Marin discussed moving to Chelsea with Bremen team-mate Claudio Pizarro, but does not believe the Peruvian's failure to fully adapt to the Premier League should have any bearing on how he fares at Stamford Bridge.
"I have done my research (by speaking to Pizarro) but I'm not afraid, it's the perfect step for me," he added.
Marin made his Germany debut in 2008 and was part of their 2010 World Cup squad. However, he has spent much of this season on the sidelines due to injury and is not assured of a place in Joachim Low's squad for Euro 2012.