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.
Mainz's general manager Christian Heidel has revealed that Thomas Tuchel has already bid farewell to the club's players, even if the coach's resignation has been rejected.
Tuchel tendered his resignation at the end of January, although that only filtered out on Saturday after they sealed their place in the Europa League next season with a 3-2 win over Hamburg.
At a press conference on Sunday, Heidel said the situation had not changed and that he expected Tuchel to respect his contract with the club.
"It's a difficult situation for Mainz," Heidel said. "We were not ready for it. Our plan was always laid out until 2015 and we were prepared for that.
"We're now willing and ready to find a solution, but we are not ready to terminate his contract. Contracts are respected at Mainz."
Heidel also revealed that Bayer Leverkusen and Schalke had both enquired about Tuchel during the season.
Leverkusen received a straight refusal from Heidel while Schalke's director of sport Horst Heldt was advised to try again in 2015.
Although Tuchel insists he will not be in charge of the club next season, Heidel maintains that he is the club's coach until further notice, although he does not want the pair's relationship to deteriorate.
"I can understand Thomas and his feelings, and his reasons, but we are still not happy with his decision," Heidel said.
"We now have to consider things and find a way by still being able to look each other in the eye.
"I will not let a bad word be said about Thomas Tuchel because I feel he is an extraordinary coach and an extraordinary person."