Gabriel has requested to exit United just four games into the Premier League season, but the club rejected his letter of de-registration and maintained that his situation can still be resolved.
Flashscore understands United continue to rate Gabriel extremely highly, but believe there are realistic limitations on how quickly a player of his age can be integrated into the first team.
His involvement in pre-season and plans to include him in the squad for the Carabao Cup game against Brighton were regarded internally as evidence of the club's commitment to his development.
United believe they have fast-tracked Gabriel as much as possible while ensuring his progression remains appropriate for his age. They are also under pressure to put together a strong season and qualify for the Champions League, making opportunities for a teenager particularly difficult to guarantee.
The club have previously fought off interest from Manchester City and have worked hard to retain Gabriel, with Jason Wilcox understood to have been particularly important in those efforts since joining United.
There is no appetite within United to blame Gabriel for the current situation, we understand. Sources close to the club remain protective of the teenager, with his age an important consideration when assessing a decision that is understood to stem from frustration over his pathway towards first-team football.
There have been reports over a period of time concerning the influence of family members and advisers around Gabriel's career, with some concerns at United about the atmosphere surrounding his development. It has also been alleged that a family member sought to make him more marketable by using the name JJ Gabriel rather than his registered name, Joseph Junior Andreou O'Cearuill.
Given Gabriel is only 15 and necessarily relies on adults to guide major decisions about his career, United do not believe he should shoulder significant blame for the current dispute.
At this stage, United sources are not entirely sure what has led to the situation spiralling so fast.
United are in a position to challenge his request to cancel his registration, and the bigger challenge is to convince him that staying at Old Trafford remains the best route for his development. Players cannot sign professional contracts until 17 or scholarship agreements until they are 16 - and Gabriel will not turn 16 until October 6th.
Chelsea are among the Premier League clubs linked, while Real Madrid and Barcelona are also understood to be interested. Bayern Munich, Borussia Dortmund, Paris Saint-Germain and Juventus have all watched him, while Arsenal, Tottenham and Man City have assessed his progress.
Gabriel was born in London and spent time at Arsenal, Chelsea and West Ham before moving to Manchester aged nine. He joined United's academy at 11 - and developed a close friendship with Cristiano Ronaldo Jr.
With his contract running until next summer, United now face a battle to keep one of their most highly regarded young players and are in immediate, urgent discussions to resolve the situation.