Inserting a buy-back clause when selling players is common practice among elite clubs across continental Europe.
However, it is surprisingly rare to find English top flight clubs requesting such clauses when moving on players. Instead, Premier League teams generally insert a sell-on fee amounting to a percentage of the next transfer fee paid for a player.
A buy-back clause provides a selling club with the first option to purchase a player back should he find himself on the transfer market again. It also gives the selling club the option to buy the player back for a set fee at any time if he is performing well for his new club. Think of it as a semi-permanent loan which suits the agenda of both the selling and the buying clubs.
While English teams have traditionally used loan moves to give their fringe players experience and first-team football, Manchester United has recently adopted the continental approach of selling players but inserting buy-back options into the agreements.
This allows the Red Devils to profit from the sale of players who haven't quite made it at Old Trafford, while ensuring that if they improve dramatically they will be offered to United before any other club.
With Jose Mourinho struggling in the transfer market this summer, it could be worth considering the following three players who all had buy-back clauses inserted into their transfers agreements when they moved away from Old Trafford.
#1 Memphis Depay
Memphis Depay arrived at Old Trafford from PSV with big expectations. Given the number 7 jersey, many predicted the Dutch winger would become the next Cristiano Ronaldo.
However, Depay's raw talent didn't suit the style of play employed by the United manager at the time - Louis Van Gaal, the manager claimed he was playing in a "too eager manner" after his Premier League debut.
Depay endured a difficult first season at Old Trafford, however he still made it on to the long list of players for the Ballon d'Or in 2015, but failed to make the shortlist. The next season, Memphis made only four substitute appearances under the new manager, Jose Mourinho, amounting to a total of 20 minutes playing time in the Premier League.
It was clear the Dutchman's time at Old Trafford was up, and in January of 2017 he was sold to Lyon for a fee rising to around €26 million. However, a clause was written into the agreement - a buy back clause. While the exact fee from the buy back clause is unknown, Manchester United has first option to bring the winger back to Old Trafford should they wish to.
At the time of Depay's transfer, Mourinho hinted that the 24 year old could one day return to Old Trafford, telling reporters at a press conference:
"He didn't succeed in his 18 months but he's very young so I think it's important for the club to complete control of this talent and we all wish he plays very, very well at Lyon and why not to come back because everyone here likes him."
Since moving to Lyon, Depay has greatly impressed, scoring 27 times in 69 appearances and maturing immensely as a player. His market value has rocketed to €45 million during his time in France, €5 million more than Jessie Lingard according to transfermarkt.
Perhaps it is time for Manchester United to activate the buy-back clause of the Dutch star?
All stats via transfermarkt
#2 Adnan Januzaj
Having joined Manchester United at the age of 16, Januzaj spent a total of six years at Old Trafford before moving on a permanent deal to Spain. The young Belgian impressed United scouts during a skills session in Brussels and swiftly moved from Anderlecht to Old Trafford where he spent two seasons playing for the Manchester United youth team.
However, at only 18 years old, he caught the eye of Sir Alex Ferguson and was promoted to the first team where he sat on the bench for Fergie's last game as United manager against West Brown. It was under the United legend's successor - David Moyes, that Januzaj really impressed.
The Belgian made his Premier League debut under Moyes and played regularly throughout the 2013-14 season, earning many plaudits. However, after Moyes' failed tenure at Old Trafford, Januzaj began to struggle under Louis Van Gaal and fell out of favor. In 2015 he was loaned to Borussia Dortmund, and in 2016 he went on loan to Sunderland.
Following these loan spells, Mourinho made the decision to sell Januzaj to the Spanish club, Real Sociedad. However, once again United inserted a buy-back clause for a very promising player who was still young and had huge potential.
Since moving to Real Sociedad, Januzaj has played regularly and shown glimpses of the talent which made him one of the most highly rated teenagers in the world. He also played and scored for Belgium in the World Cup, curling in a wonderful goal against England.
Should his form continue, a return ticket to Old Trafford is a distinct possibility for the 23 year old.
#3 Sean Goss
A young midfielder with bags of potential, Sean Goss came up through the Manchester United youth ranks before moving to QPR in 2017. Born in Germany, Goss was signed by Manchester United from the Exeter youth team at the age of 17. He played for the United youths for three years before graduating to the full squad in 2015.
While the midfielder never played a competitive first team game for United, he appeared in a preseason game in 2015 and was an unused substitute during the 2015-16 Premier League season. However, he spent most of his two years in the United full team playing for the reserves.
In 2017, Goss moved to Championship side QPR for a fee of around €700,000. He struggled to break into the first team at Loftus Road, making only six appearances before moving on loan to Glasgow Rangers in January 2018. The midfielder lit up the Scottish Premier League during the second half of last season, making 13 appearances and scoring twice for The Gers.
While still only 22 years old, Goss has started showing signs of the potential which encouraged United to include a buy-back clause into his contract. While it is perhaps a little early for a return to Old Trafford, if the starlet can continue his superb form displayed during the second half of last season, the Red Devils may need to seriously consider activating the clause they placed in his transfer to QPR.