Celtic lost one of their stars in the summer as central defender Kristoffer Ajer departed Parkhead and the Hoops when he was sold to Premier League side Brentford.

After months of speculation, with reports of failed bids from Bayer Leverkusen and Norwich, Ajer sealed his permanent move to the London-based club and Australian head coach Ange Postecoglou lost a top player in the heart of his defence.

The Hoops landed Ajer from Norweigan side IK Start for a measly £540k in the summer of 2016 and he established himself as a regular starter over the years at Parkhead. He played 176 matches in all competitions for Celtic, scoring seven goals from centre-back and eventually earning himself his big-money switch to Brentford.

Last season, Ajer caught the eye with a series of impressive performances. He averaged an excellent SofaScore rating of 7.15 as he started 34 matches in the Premiership. Celtic kept 17 clean sheets in those games, with Ajer winning 62% of his duels on the pitch. That ensured he made 2.7 tackles and interceptions and 3.3 clearances per game.

The towering Norweigan also went through the entire campaign without committing a single recognised error leading to a shot or goal. This does not include penalties as one spot-kick given away was a small blot on an eye-catching season for Ajer.

Speaking in 2020, Alex McLeish labeled Ajer “influential” and likened him to Liverpool colossus Virgil van Dijk. The ex-Villa coach told Football Insider:

“I go back to that St Johnstone game, you see sometimes when it’s not going for Celtic, and the game’s in its dying embers, and then all of a sudden you see Ajer striding up the pitch trying to inspire like Roy of the Rovers.

“Running from defence, augment the attack and then it leads to a goal – these are inspirational moments, and he is an inspirational, influential player for Celtic. Like Virgil van Dijk, he came to Celtic, and we all know what happened next.”

His superb form in the Premiership, highlighted by these comments and the aforementioned statistics, secured him his transfer to the Bees this summer. The Premier League side paid roughly £13.5m for his services, which shows that Celtic pulled off a transfer masterclass with the defender.

They bought a teenager centre-back with 61 matches of senior experience for £540k and developed him into a £13.5m player. This is a profit of almost £13m for five years of work behind the scenes on the training pitch and in games each week in the Premiership, sending a message to other young players who could see Ajer's progress and want to go on a similar journey.

This means that Celtic made a healthy turnover on Ajer whilst potentially giving themselves a better chance of landing talented young players in the future. They could be given a boost in the transfer window as they can point to players like Ajer as examples of the excellent work they can do.

AND in other news, £7.4k-p/w Celtic wizard's value has soared 177.7% since January, Postecoglou loves him...