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.
Middlesbrough have handed a trial to former Dynamo Kiev midfielder Carlos Correa after being recommended by club legend Juninho.
Juninho still has strong ties with the club he spent three different spells with and, although now president of Ituana in his native Brazil, he is looking to help his former club too.
Now he has recommended two midfielders who he feels can help Boro and, of the two, Correa has an impressive CV having just ended a six-year stint with Ukrainian giants Dynamo Kiev.
The 31-year-old is a set-piece specialist, and has also enjoyed spells with Palmeiras and Flamengo.
The second player is 23-year-old Eduardo Favretto - also known as Dudu. He has spent most of his time in the lower leagues in Brazil, but has played for Lucchese in Italy.
"The relationship between Juninho and the club is very strong," said manager Tony Mowbray.
"I think Juninho knows the standard of player we need. While we're not in the Premier League, we're still looking for players who are good enough to get us back there. There have been some discussions and we're hoping to have a look at them and see what sort of qualities they possess and if they suit our needs.
"One of them has been playing in Kiev for the last five years but is now back in Brazil and Juninho feels he has the required talent.
"For me, it's not just about talent, it's about the balance of our squad. There's no point bringing in a player who upsets the balance of our squad. But if he has the talent, we will have a look at that.
"He might have exceptional talent but might not have the discipline required to play in England, for example. Let's wait and see.
"We want to look at them and see if their qualities are what we want to add to the squad.
"I would hope there will be another face or two to add to the squad, which will be good for the supporters to see if they want to come along."
Chief executive Neil Bausor revealed that the opportunity was first mooted when he received contact from Juninho a few weeks ago.
"Juninho highlighted some players to me that he thought would fit with Middlesbrough Football Club and we've been working over the past two weeks to bring the players across," he said.
"It's fantastic that we've still got such strong links with a great player from our past and as a result of that relationship we have these two players visiting us this week."