Cardiff City boss Ole Gunnar Solskjaer said the attraction of playing in the Premier League could prove too much to hold on to captain Steven Caulker.
The club have confirmed they have accepted a bid from Queens Park Rangers for the England international.
The 22-year-old's release clause was triggered by the club's relegation from the Premier League.
"The lure of the Premier League might be too much for us to hope that he stays here," said Solskjaer.
The Bluebirds manager said only a bid from QPR has been accepted by the club, but it is understood that other clubs could be interested in signing the central defender.
"The clubs have agreed a fee, it's up to Steve to decide," said Solskjaer.
"He enjoyed the season here, he played every single minute last season and he did exceptionally well."
Caulker trained with his team-mates on Friday and Solskjaer said he wants to get any deal done as soon as possible so he has a settled squad to work with.
Neither club has disclosed the size of the bid, but it's believed to be in excess of £8m which is the figure required to trigger a transfer.
Caulker joined the Bluebirds for around the same amount following their promotion to the Premier League in the summer of 2013.