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.
Fabio Capello has rejected reports that he has been approached about becoming the next manager of Chelsea.
Benitez's future as manager has been the subject of intense speculation over the last few days after his outburst against the club and the club's fans following last week's FA Cup win at Middlesbrough.
A number of names have been linked with the Chelsea post in the wake of Benitez's criticism, with former England boss Capello the latest candidate to emerge on the radar.
However, Capello insists he has received no offer from Chelsea and is focused on leading Russia to the 2014 World Cup finald.
"I am only thinking about reaching the World Cup with Russia," Capello told Italian radio. "At the moment, I am not thinking about anything else.
"I have received no offer."