Celtic boss Tony Mowbray is refusing to reveal whether Gary Caldwell will be sold during the January transfer window.
The defender's contract is due to expire at the end of the season, leaving him free to join another club without a transfer fee.
Middlesbrough have been linked with a move for the 27-year-old, with former Bhoys boss Gordon Strachan now at the helm at the Riverside.
It has been speculated last Sunday's Old Firm clash might have been Caldwell's last for the club, but Mowbray is giving little away.
Mowbray insists the club still control Caldwell's future and that they will have the final say on whether he goes in January.
"I don't know if it was Gary Caldwell's last game in a Celtic jersey," he told the Evening Gazette.
"We are all very aware of his contract situation and if there are any conversations to be had, we will have them.
"What I do know is that we will be in control of whether Gary stays at Celtic or goes.
"He is our player, he is under contract and we will decide what is best for this football club, first and foremost.
"I am in the market for quality footballers and I have to wait and see what happens there."