Celtic have enjoyed great success in the transfer market over the years having been able to unearth gems before selling them on for significant fees.

Who are Celtic's biggest ever sales?

The Hoops do not have Premier League money to be able to afford to splash out multi-millions on players to bolster their squad and this means that their player trading is incredibly important in order to generate funds.

There have been several examples of excellent pieces of work by the Bhoys, including their five biggest sales which saw them identify young talents and develop them into sellable assets.

Player

Fee received

Jota

£24.9m

Kieran Tierney

£23.1m

Moussa Dembele

£18.8m

Odsonne Edouard

£13.9m

Virgil van Dijk

£13.4m

Fees via Transfermarkt.

One player whom the club played a blinder with was central defender Kristoffer Ajer, whose value soared during his time at Parkhead.

Ange Postecoglou, who arrived towards the end of his spell in Scotland, also secured a masterclass with the timing of his sale as the Norway international has not had the best of luck down south.

How much did Celtic sign Ajer for?

Ronny Deila signed the then-17-year-old for a reported fee of up to £650k from IK Start in 2016 after the teenager had already racked up an eye-catching 61 first-team appearances and scored 14 goals for the Norwegian side.

He had already emerged as a fantastic talent at such a young age and, interestingly, arrived at Parkhead as a versatile midfielder or forward player.

Ajer had scored seven goals in 14 matches as a centre-forward for Start and the rest of his outings came in a variety of midfield positions.

Brendan Rodgers opted to send him out on loan to Kilmarnock during the 2016/17 campaign and he racked up 16 Scottish Premiership appearances.

His experience during that loan spell then set him up to break into the Northern Irish head coach's squad for the 2017/18 season. Ajer went on to play 34 times in all competitions for the Hoops that term and all bar two of his appearances came as a centre-back, which was a far cry from his outings as a number nine for his former club.

The 6 foot 5 colossus was converted into a defender by Rodgers, who seemingly saw that he could excel in that position instead of as a striker or an attacking midfielder, and became a mainstay of the backline at Parkhead for a number of seasons.

Ajer ended up with 176 first-team appearances and chipped in with seven goals and seven assists for the Scottish giants during his time with the Bhoys prior to his eventual exit in the summer of 2021.

How much was Ajer worth at Celtic?

Football Transfers rated the Norway international's Expected Transfer Value (xTV) at €25.5m (£21.8m) in July 2021, a whopping 2,050% increase on the initial £650k that was spent to secure his services in 2016.

Postecoglou arrived at Celtic that summer and sanctioned a sale for the towering defender as he joined Premier League side Brentford for an initial fee of £13.5m, although there were undisclosed add-ons that could increase that figure.

This means that the Hoops made a staggering profit of 1,977% on the giant centre-back, who enjoyed a sublime final campaign with the club in the 2020/21 season.

Ajer, who was described as "faultless" by former boss Neil Lennon, averaged a fantastic Sofascore rating of 7.15 across 35 Premiership matches for the Scottish giants as he caught the eye with his strong defensive displays.

The 25-year-old made 2.7 tackles and interceptions per match and won 62% of his duels, as per Sofascore, showing that the former IK Star prospect was able to make multiple defensive interventions per game to cut out opposition attacks.

His performances were good enough to convince Brentford to splash out a minimum of £13.5m to secure his services, a deal that turned out to be a masterclass from Postecoglou.

How much is Ajer worth now?

At the time of writing, Football Transfers rate Ajer's xTV at €10.3m (£8.8m), representing a staggering drop of 60% from the €25.5m xTV he had at the time of his move to the Bees two years ago.

This shows that the Australian head coach, who is now the manager of Tottenham in England, sold the brute at the perfect time.

Celtic were able to cash in on him whilst his value was high, making a gigantic profit in the process, and enjoyed his talents on the pitch for a number of years before that.

Why is Ajer worth that much?

The 25-year-old's market value has dropped over the last two years as he has struggled with form and injuries during his time with Thomas Frank's side so far.

Ajer averaged an unimpressive Sofascore rating of 6.84 across 24 Premier League appearances during his debut campaign for the Bees, which was the 11th-highest score within their squad and the fourth-highest rating out of their centre-back options.

This is an indication that the former Celtic star was not one of Brentford's top performers or one of the best within his own position, despite his previous impressive displays for the Scottish giants.

His 2022/23 campaign was disrupted by having surgery on his hamstring and the Norwegian ace only managed to appear in nine Premier League matches throughout the season and averaged a dismal Sofascore rating of 6.44 in those games.

He ranked 24th out of his club's 25 players based on his average Sofascore rating last term as the central defender proved himself to be an unreliable player for Frank, both in terms of his worrying displays on the pitch and his lack of availability due to injury.

All of these factors have led to his market value plummeting over the last two years and he is now only worth a fraction of what he once was at Parkhead.

Therefore, Postecoglou and Celtic turly hit the jackpot by deciding to sell him when they did.