Celtic have been unable to unearth a number of stars in recent years as they have plucked out talented young prospects for modest fees before selling them for a significant profit.
Who are Celtic's most expensive sales?
The Hoops have raked in millions from player sales having proven to be an excellent landing spot for promising talents to come and showcase their ability as part of a dominant side in Scotland.
Player sold
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.
The club's five-most expensive sales in their history highlight their ability to develop signings as only one of the five – Kieran Tierney – came through the academy system at Parkhead.
Another player whom the club, and manager at the time Ronny Deila, played a blinder with was Scottish central midfielder Stuart Armstrong, whose value soared during his time with the Hoops.
Deila, who won two Scottish Premiership titles and one League Cup in Scotland, snapped up the talented gem from Dundee United and it turned out to be an outstanding piece of business by the Norwegian tactician.
How much did Celtic pay for Stuart Armstrong?
The Hoops reportedly splashed out a fee of £1.6m to sign the technically-gifted ace from the fellow Scottish side during the January transfer window in 2015.
They had two bids rejected by Dundee United earlier that window and faced competition from Premier League team Burnley but were ultimately able to secure his services for the aforementioned figure, which was said to be too expensive for the Clarets as they backed away from a possible deal.
Celtic signed the 22-year-old after he had proven himself to be a reliable attacking outlet at Premiership level with United.
Armstrong racked up 21 goals and 31 assists in 150 appearances for his former club and provided a regular threat at the top end of the pitch during his final two league campaigns.
The versatile gem, who was deployed out wide or in the middle of the park, produced eight goals and seven assists in 36 Premiership matches throughout the 2013/14 season. He also managed an outstanding three goals and three assists in five SFA Cup clashes that term.
Celtic's attention was then caught by his performances during the first half of the following campaign as the central midfielder scored six goals and assisted six in 20 league matches for United, which was an average of one goal contribution every 1.67 matches – better than his average of one every 2.4 outings in 2013/14.
This convinced the Hoops to splash out £1.6m to secure his signature and it turned out to be a fantastic decision as Armstrong enjoyed a brilliant spell with the Scottish giants.
How many goals did Armstrong score for Celtic?
The Scotland international, who has been capped 43 times by his country to date, went on to score 28 goals in 144 appearances for the Bhoys during his three-and-a-half-year stint at the club.
Armstrong, however, did not enjoy the best of starts to his career with Celtic as he managed just one goal and four assists in 15 Premiership matches over the second half of the 2014/15 campaign.
The attack-minded midfield wizard got his feet under the table ahead of the 2015/16 season and went on to produce four goals and seven assists in 25 league outings for the Scottish giants.
His best form in a Hoops shirt came during the following campaign as Brendan Rodgers arrived at the helm in 2016 and got the former Dundee United star firing.
Armstrong ended the 2016/17 term with an outstanding 15 goals and seven assists in 31 league matches for the club, which worked out as an average of one goal involvement every 1.41 outings.
In 2017, Rodgers lavished praise on the central midfielder and described him as a "powerful" player who has "everything" to his game. The Northern Irish tactician said that he was impressed by Armstrong's raw materials and went as far as to say that he was a "joy" to work with in Glasgow.
He did not hit quite the same levels the following year, as Armstrong scored three goals and provided five assists in 27 Premiership games, but that did not stop Premier League side Southampton from making a move for him.
How much did Celtic sell Armstrong for?
The Hoops eventually cashed in on Scotland international during the summer transfer window in 2018 as the Saints snapped him up for a reported fee of £7m.
Sky Sports claimed that talks over an improved contract at Parkhead had stalled with the goalscoring midfielder and that opened the door for the English club to secure his services.
The £7m fee that they received for him did, however, mean that the player's market value soared by a whopping 338% from the initial £1.6m they paid Dundee United for him during his time in Glasgow.
This shows that Deila struck gold for Celtic with his deal back in 2015 as Armstrong went on to become an excellent performer under Rodgers and earned the club a big payday just over three years later.
Where is Armstrong now?
The 31-year-old is still with Southampton and is currently playing Championship football at St. Mary's after he made 149 Premier League appearances for the club.
Armstrong produced 16 goals and 12 assists at the top level of English football and has played 175 games for the Saints in total since his move in 2018.
Football Transfers now rates his current Expected Transfer Value at €4.8m (£4.1m) with his market price having plummeted towards the twilight of his playing career.
Overall, Deila's decision to sign Armstrong from Dundee United was a shrewd one that resulted in Celtic enjoying his talents on the pitch for a number of years before raking in a big fee for his services before his value started to drop.
It also showed that there is value to be had in picking up young Scottish players from fellow Premiership teams and that the club does not always need to look abroad to find up and coming talents.