Having done some research, it seems to me Celtic are desperate to sell. And it looks like they tried hard last summer to get £25m out of Everton for the kid too.
That's no reflection on Tierney's ability either, it's a reflection on the reality of Celtic's financial situation and the intentions of the people running the club.
It's a great time for us to buy: He's off the back of his first sub-excellent season, owing to a double-hernia problem he suffered through for most of the season because he was desperate to help the team he loves win an unprecedented "treble-treble." He had an operation 2 days after the Cup final, in which Celtic did in fact seal a treble. Tierney didn't play but he trained right up to the last session to try and make it, but the hernia problem proved too much.
I can't talk in great detail about his game; I haven't seen too much of him, but it seems Tierney is a real throwback to times gone by in terms of his agression, passion and no-nonsense style on and off the pitch. He is adored by the Celtic fans, partly because he's one of their own, but also because of the aforementioned qualities.
He has 150+ games for Celtic and only recently turned 22. He's won tons of trophies, played Champions League; marked Messi, Mbappe and Robben at different times, he was double (SFA & Football Writers') young player of the year and in the SPL team of the year in each of his first three seasons, until this one.
Yes, the standard is poor, but he's clearly a bit special.
Having watched what's available on YouTube of his game, the kid can clearly time a tackle. There's also an endless reel of fantastic crosses curled, smashed, and lazer-guided into the path of a forward. Lots of examples of his ability to get on the outside, even in games against Champions League opponents, and get crosses in. He has a poweful running style that usually means an improvement in speed occurs around the age he is now as his muscles fully develop.
He would be some signing. If the club can do a deal similar to what has been reported: £15m + Carl Jenkinson and a loanee or two, then he would prove to be a steal. He's not as proven as the fullbacks that have gone for £50m+ but I suspect he would prove himself in England very quickly.