"Players always decide their future whether they are contracted or not. If players feel their futures lie elsewhere, I can't do anything about that. But nobody has said that and I have not had to deal with it.
"In a way I am sympathetic. But we make our beds and we all have to lie in it. It's a big bed where John's concerned.
"We would need to take all those things into consideration. We will look at what John wants to do and I will need to sit down with him."
Hartson still has two years on his Celtic contract and his agent Jonathan Barnett has laughed off rumours he could move to Swansea City
"He has got two years remaining on his Celtic contract so why wouldn't he see that through?" said Barnett. "He is enjoying his time up there.
"I have been reading and listening to speculation for the last 10 years or more but if I believed everything that I read, heard and saw then I would be mad. I have not heard about Swansea but it would be totally stupid to think he could go there."