Manchester United could be set to sign Kieran Tierney from Celtic.

That is the opinion of former Hoops star Stiliyan Petrov.

He believes a club like United would have no issues putting together the funds to sign Tierney.

While Celtic do not want to lose their left back, a big money move would be too hard to turn down.

"You don't go under the radar if you are consistently one of the top performers," Petrov said of Tierney to the Daily Record.

"I don't know if it will be this summer or next but I do think at some point Celtic's resolve will be tested.

"And if a huge offer comes in the reality is you have to take it. It will take big money to get him. I don't know how much but it will be no problem for a Man Utd or whatever.

"The boy just has to keep doing what he is doing. Getting into the Champions League can be so important for his development.

"He has the potential to go on and be world class. He could go to a Man Utd or any other top-level club because he's been brought up having to play under pressure.

"Like all good players he has not just survived in that environment but has flourished and those who have the temperament to deal with that are the guys who make it to the top.

"He has shown he can cope at European level. In the Champions League he has been excellent. But it is also about the way he behaves on the pitch. He has shown he is a leader.

"He has captained his country and he has captained Celtic. That is special for being only 21.

"He will get better all the time. As an ex-Celtic player and a Celtic fan I want him to be here for as long as possible. But that is not how football works."