Brendan Rodgers has admitted he is unsure whether Kieran Tierney will still be a Celtic player next season.
The 20-year-old has been a key figure for Celtic this season, and recently won the Scottish Football Writers' Young Player of the Year award for the third successive campaign.
Celtic are on course for their second domestic treble in as many years, but Rodgers says he cannot offer any guarantees regarding Tierney's long-term future.
He said: "I don't want to say either or really. The time when players were not for sale is long gone.
"The kid has signed a long-term deal and you can see the happiness he has here.
"But there's also a moral aspect to it, where if a player is on X amount of money and he's offered five X by someone else and the club also has a big offer then it's something that will be spoken about.
"Kieran, because of his age and his talent, is always going to be linked with other clubs. There will be suitors watching him. It is a short career and it's only right that you're mindful of that."
While his manager accepts wealthier clubs will show an interest in the left-back, Tierney himself insists he is happy at Celtic Park.
He said: "It has happened (transfer speculation) during most windows since I broke through - it's good for me. If somebody wants to buy you that means you're doing something right.
"When big teams are looking at you it's flattering. It doesn't bother me or distract me because I'm enjoying myself. I'm playing for Celtic so I'm happy.
"I'm not in any rush at all. I had four years left on my last contract and if I wanted to leave I would have chosen to run that down. Instead, when the club offered me six I was happy to sign."