While tensions between Gabriel’s camp and United had been simmering for a number of months, sources have told BBC Sport the player’s decision to seek a move away was ultimately triggered by his non-inclusion in Michael Carrick side for the Champions League encounter with Azerbaijani champions Sabah FK on 10 September.
The youngster’s camp had expressed a desire for Gabriel to be used as a substitute against Sabah – which, on paper, was the easiest of United’s league-phase games.
Sources say the prospect of the Londoner coming on against Brighton in the EFL Cup on 16 September was also discussed, with United officials subsequently insistent that was the plan.
Had he played in either match, Gabriel would have become United’s youngest ever player.
However, by the time the encounter with Fabian Hurzeler’s side arrived, the striker had already told the club of his intention to quit and had left the country.
Gabriel could not play against Sabah because he had not been registered on United’s Uefa A list of players when it was announced on 3 September. The precise reasons for this have not been made clear.
It did not prevent him scoring a hat-trick in a Uefa Youth League game against them at Leigh Sports Village earlier on 10 September. While he has not been back to United since, it is not clear whether anything significant happened after that game.
For their part, United believe they made it clear they view Gabriel as immensely important to their first-team future, even though sources have indicated the player did not report for the start of the academy’s pre-season training schedule at the beginning of July – a week earlier than the senior squad – despite being asked to do so.
Sources also say they lobbied the Premier League to allow the forward to use “JJ Gabriel” on the back of his shirt – which they believe underlined their commitment to the academy prospect.
Gabriel’s real name is Joseph Junior Andreou O’Cearuill – but he is reported to have changed his name for commercial purposes.
In addition, United say they have provided Gabriel with first-team care and services – included regular meetings with senior coaches and nutritionists.
That he was included in the senior team photo is also viewed as further evidence of their commitment to his development and transition into first-team football.