The Dutchman stood firm and refused to entertain the idea of joining the Red Devils in 2022, even when his current club opened the door to an exit and accepted a bid from Man United.
Erik ten Hag - who managed De Jong at Ajax - has never lost sight of his former protege, and there have been suggestions that Barca's volatile financial situation could see Man United reignite their interest.
Xavi's departure as head coach and the appointment of Flick has also thrown some players' futures into uncertainty, but president Joan Laporta has insisted that the Blaugrana are under no major pressure to sell their big-name stars.
Now, journalist Roger Torello claims that both Barcelona and Flick view De Jong as a player who must not be sold under any circumstances, ending Man United's pursuit for the time being.
De Jong contributed two goals from 30 matches for Barcelona in an injury-hit 2023-24 season, but he was called up to the Netherlands squad for Euro 2024.
Speaking of managers making key transfer decisions, Chelsea's Enzo Maresca has apparently vetoed the idea of making a move for Napoli striker Victor Osimhen in the summer transfer window.
After being confirmed as Mauricio Pochettino's successor, Maresca did not take long to welcome his first new recruit to Stamford Bridge, signing ex-Fulham man Tosin Adarabioyo on a free transfer.
A new striker is now at the forefront of the Blues' thinking, and the West London giants have long been linked with Napoli's talisman Osimhen, whose departure from the Partenopei is imminent.
However, reports in Italy - via football.london - claims that Maresca is not keen on bringing Osimhen to Stamford Bridge this summer, in spite of the Nigerian's exceptional scoring record in Serie A.
The ex-Leicester City manager apparently does not view Osimhen as a striker who can play the Harry Kane role, dropping deep and linking up with his teammates, which is what he is after in a centre-forward.
Furthermore, the ex-Lille man could cost in excess of £110m to prise away from Naples this summer, and Paris Saint-Germain are currently thought to be at the head of the queue.
Elsewhere in London, Tottenham Hotspur's search for defensive reinforcements has reportedly taken them to Nottingham Forest and Murillo, one of the stars of their 2023-24 season.
Arriving from Corinthians in the summer of 2023, the 21-year-old earned numerous plaudits for his assured defensive displays and qualities on the balls, setting up two goals in 32 Premier League matches.
Murillo's contributions were crucial in keeping the Tricky Trees afloat in the Premier League, but in spite of his long-running contract until 2028, Forest could be fighting a losing battle to keep hold of him.
According to Football Insider, Tottenham are the latest team to show an interest in the 21-year-old, whom Forest could be under pressure to sell due to the threat of more financial sanctions.
However, Spurs are just one of a handful of teams tracking Murillo, who is also on the radar of PSG, Liverpool, Manchester United and Chelsea, the former two of whom could offer him Champions League football.
Meanwhile, Murillo would have to settle for Europa League action at Spurs, Europa Conference League minutes at Chelsea and no continental football whatsoever at Old Trafford.
Sticking with Tottenham's search for more rearguard members, the Lilywhites could apparently face competition from three of their Premier League rivals to sign Feyenoord's Lutsharel Geertruida this summer.
The Netherlands international is one of a handful of former Arne Slot players tipped to reunite with the newly-appointed Liverpool boss at Anfield, especially as the Reds are known to be searching for defensive options.
A right-back who is also comfortable centrally, Geertruida is only under contract with Feyenoord until 2025 and was spotted attending Premier League last season ahead of a potential move to English shores.
According to AD, all of Liverpool, Tottenham, Newcastle United and West Ham United are showing an interest in Geertruida, who was named in the Netherlands squad for Euro 2024.
Feyenoord and the 23-year-old's camp have apparently failed to reach an agreement over a new deal, meaning that he will have to be sold this summer lest the Dutch giants risk losing him for nothing in 2025.
A move to RB Leipzig was supposedly on the cards last summer, and the Bundesliga powerhouses were prepared to pay £27.7m for his services, but negotiations ultimately broke down.