Christie has been the subject of interest from Liverpool and Swansea City in recent weeks.
Casey boss John Hughes said the club would most likely sell Christie if the right offer comes along.
"It was Liverpool last week, Swansea this week, and I've no doubt it will be someone else next week," Hughes said.
"It's no surprise to me. Ryan is a really talented footballer and we need him in the team.
"We can't afford to lose him, but I'm sure if the money was good then we would sell him.
"But I think part of it would be that he would have to stay for another year here on loan.
"We would never stand in the kid's way if he can go and play in the English Premier League."