Stilian Petrov's agent claims Gordon Strachan and Neil Lennon will be wasting their time in trying to persuade the Bulgaria international to stay at Celtic.
The Parkhead manager and captain have urged the midfielder to reconsider his transfer request, but the player is adamant he will quit after seven years with the club.
Representative Tony McGill has been directing any interest in Petrov from England and the continent straight to Celtic.
But the agent believes the 26-year-old will be leaving the Hoops sooner rather than later.
McGill said: 'Stilian is not going to stay. He has been thinking about this for six months now.
'Obviously, Gordon Strachan genuinely wants him to stay - as will all his team-mates.
'But the bottom line is, now Stan has put it in writing, it is a weight off his shoulders.
'I have had contact from other agents representing various clubs all over Europe and these have been directed to Celtic.
'I have not done anything wrong and it's out of my hands until - if and when - Celtic accept an offer from a club.
'There were clubs in for Stan in January when he had nothing to do with me at the time.
'I wasn't his agent then but it doesn't matter who his agent is if he decides to leave. The club will have to let him go.'
John Hartson has also been linked with an end-of-season exit but Strachan has now spoken with the striker's agent, Jonathan Barnett.
The Wales international had appeared set for a move south to be closer to his family.
But now his representative has hinted the 31-year-old could stay in Glasgow.
Barnett said: 'John's situation was discussed but we talked about many other issues.
'He's contracted to Celtic and nothing has changed.
'John's domestic situation is a concern, but, hopefully, that will all be resolved and we'll get on with life.'
Meanwhile, Atletico Madrid appear to have abandoned their interest in signing Celtic star Shunsuke Nakamura.
The 27-year-old Japan international has been linked with a summer move to Spain.
But Raul Garcia, assistant to Atletico sporting director, Tony Munoz, said: 'Tony makes the final decisions on the players the club signs and, from talking to him, Nakamura won't be coming here.'