Cagliari president Massimo Cellino has confirmed he will allow Radja Nainggolan to leave the club this summer, but only if his asking price for the midfielder is met.
Belgium international Nainggolan has been a long-term target for Serie A champions Juventus, while he has also been linked with a move to Russian side Zenit St Petersburg.
Cellino is prepared to let the 24-year-old join a bigger club for next season, but has called on the player's suitors to stump up €18million (£14.6m).
"I promised Radja that should an offer from a top club arrive, I would allow him to leave," Cellino said to Corriere dello Sport.
"But the offer needs to be a big one, not inferior to 18m euros."
Nainggolan, who joined Cagliari two years ago from Piacenza and is under contract until 2014, scored once in 37 Serie A appearances for the club last season.