Celtic: Top clubs will eye Kieran Tierney in Champions League - Kris Commons

Kieran Tierney (right) captained Celtic against Kilmarnock

Top clubs will wait to see how Kieran Tierney performs in the Champions League before considering a bid for the left-back, believes Kris Commons.

But Commons thinks the 20-year-old "could be the captain of Celtic for the next 15 years" if he stays.

"I think they will be waiting to see how he is in these Champions League games," said of his former team-mate.

"If they are going to spend £10-30m on a player, they need to know he's able to play against Ronaldo and Bale."

But Commons points out that Tierney, a product of Celtic's youth system, has already impressed at Champions League level and will be a key player as they attempt to beat Astana of Kazakhstan to reach the group stage.

"He played against Raheem Sterling and more than matched him there and he was still a teenager, 19 I think," the former Celtic midfielder told BBC Scotland.

"If they do get to the Champions League, that's where he is ultimately tested, watched by these big guns, because they need to tick all the boxes."

Tierney stood in for the suspended Scott Brown against Kilmarnock to become Celtic's youngest-ever captain earlier this month.

Commons believes that the defender is not quite ready to assume such responsibility full-time.

"To be a captain of a club like Celtic you need to have that bit of edge, which he shows on the field, but off the field he is still a quiet, good, honest boy," said the former Scotland midfielder.

Kieran Tierney scored for Celtic in a 3-3 draw with Manchester City

"As a captain, you have to be the manager on the park. That will come with experience.

"But he is a Celtic fan and you see from the way he celebrates. It's like he is on the terraces. He was a ball boy. He is living the dream."

Commons, 33, thinks Tierney, who already has four Scotland caps, has a great future ahead of him.

"Defensively, he is one of the best I've seen at his age," he added.

"He seems to get better every single week and it's his work ethic, not just on the park, off it as well. He is forever working on his weaknesses in training.

"He has a great relationship with all the players and coaches, they want to keep making him better.

"And, let's not forget, he's broken his leg twice in the last two years.

"For him to maintain fitness levels and that amount of enthusiasm is impressive and, for a guy who's broke his leg twice, he still won't back out of a challenge."