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.
Huddersfield have signed Reading striker Simon Church on a one-month loan deal.
Manager Simon Grayson has swooped for the 23-year-old to boost his injury-hit attack and he could make his Town debut against Barnsley on Saturday.
Grayson told the club's official website, www.htafc.com: "Simon is a player we have monitored for some time and he adds genuine top-level quality to our striking department.
"We looked at bringing him to the club during the summer but at that stage Reading wouldn't let him out.
"The current strikers we have at the club have done a tremendous job so far but we've suffered some injuries in that area recently and we felt the time was right to bring Simon in, especially as James Vaughan is suffering from a troublesome thigh strain.
"All being well he will train with the squad on Thursday and comes into my thinking for Saturday's game at Barnsley."