Russel Slade has said it will be best for all parties if defender Juan Cala left the club in January.
Cala took to social media to highlight that he was training with the academy.
"It was all agreed we would like to move Juan in the January window, if at all possible," said Slade.
"That was the agreement with his agent so he knew where he stood and so they could do something about that in the short term in terms of finding another football club.
"Juan is one of those players who we spoke to, with his agent, a good three or four weeks ago with regard to his situation."
Centre-back Cala joined Cardiff from Sevilla in February 2014 and featured regularly in the Premier League last season.
But he has made only one Championship appearance this season and has reacted angrily on Twitter.
He wrote: "I just want the situation to be sorted out and to play here on in another club ASAP!! Thank you for support."
Asked whether Cala was disruptive, the Cardiff manager said: "That's not for me to comment on - that's an internal problem and we are not going to discuss those finer details."
Slade said it would be an "executive decision" as to whether the club would demand a fee for the player.
He also revealed that Bluebirds owner Vincent Tan did not tell him to leave Cala out of the first team squad.
"That's not really the case . . . I have said from the very beginning the owner is entitled to his view, his opinion and I am sure he will stress that in time.
"But it was a management decision and we move on."