Former Celtic striker Frank McGarvey has insisted that if Kieran Tierney has ambitions of succeeding in Europe he will need to quit the Parkhead side – but all in his own time.

McGarvey described Tierney as the best left-back in Britain and the best that Celtic have seen since the era of Lisbon Lion Tommy Gemmell.

Tierney has been widely scouted over the last 20 months as he has come to prominence at Celtic. Manchester United are reported to be weighing up a summer move for the Scotland internationalist – although McGarvey believes Tierney would be a better fit for their noisy neighbours.

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“Right now he is the best left-back in Britain, bar none,” said the former striker. “To me a club like Manchester City who look like they could win something in Europe and who play in a style that suit Tierney would be an ideal club for him.

“Tottenham, too. They play an attacking style of play and we have seen them get better and better of late. To me that is the kind of team where he would slot right in but ultimately it is up to the boy himself.

“The next step he takes in his career is life-changing. Right now Celtic are all he knows and all he has ever known. He has been at the club since he was at primary school, he has gone through the ranks all the way to the first-team and he is still settled at home with his parents.

“Only he can decide what he wants. If it was me, it would come down to European football. The gap is getting wider all the time. Celtic are not going to invest in the team to the extent that it will make a huge difference to what they do in the Champions League.

“As a player that would be my motivation. But he seems like a sensible lad and he will know what is best.”

Given some of the finances that do the rounds when the transfer market opens, one can only speculate to the fee that Celtic would demand for any prospective sale of Tierney, whether now or further down the line.

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For McGarvey, though, going to the right club with the right people around him is critical. At one brief stage in his career McGarvey was Scotland's most expensive player as he made the switch from Liverpool, where he last just ten months, to Celtic.

“When I moved to Liverpool it was a disaster because I just didn’t feel like I fitted in there,” he explained. “It is an enormous decision to make.

“If you are happy and settled then there is nothing better and that shows every time you walk onto the pitch. It is very difficult if you don’t that.

“But one thing is for sure and that is that Celtic will be significantly weaker if Tierney was to go. They’d be in rude health financially but they would struggle to replace him with similar quality.

“Who knows what he is worth in today’s market? You see crazy money spent on players. Celtic’s businessmen will ensure that they are pretty well compensated when the time comes – or if the time comes – but there is no doubt that every top club in the Premier League will know what Tierney has got.

“He has everything that you want for a left-back. He is an athlete. He can defend, he can attack, he can cross and we have all seen that he can score. He has the lot, in the same way that Tommy Gemmell had the lot. I honestly think he is in that class.”