Real Madrid have emerged as favourites to win the race for his signature, according to The Athletic, in the latest twist to a saga that has gripped Manchester United's academy this week.
Gabriel, 15, has scored 29 goals in 32 competitive matches for United's under-18 side and has since stepped up to the under-21s, where he has two goals and two assists in two Premier League 2 appearances.
On Tuesday, multiple credible outlets reported that Gabriel had informed United of his wish to leave as soon as possible, with the relationship between the club and his family said to have broken down. His contract runs until the end of the season, but Gabriel is understood to have formally requested to be released via a written letter.
The Athletic had previously reported that the teenager was being chased by Real Madrid, Barcelona, Chelsea, Bayern Munich and Paris Saint-Germain, but now says Real Madrid are in a strong position to win the race.
The Spanish club are said to have been working discreetly on the deal for several months, with chief scout Juni Calafat closely involved.
Only a small number of people within the Real Madrid hierarchy have reportedly been aware of the situation, a reflection of Fifa's strict rules around transfers involving players under 18, which have previously led to sanctions for clubs found to have breached them.
Signing Gabriel is seen internally at Real Madrid as a strategic move that looks beyond his current academy level, with the long-term plan reportedly involving a pathway into reserve side Real Madrid Castilla, while also making him eligible to play in the Uefa Youth League with the club's junior team.
Ordinarily, a move abroad would not be possible until Gabriel turns 18, but an exception exists for players who hold an EU passport, allowing a transfer at 16 instead.
Gabriel's father, Joe O'Cearuill, is a former Republic of Ireland international, while his mother is of Cypriot descent — meaning the teenager has a route to European Union citizenship that could clear the way for an earlier move than would otherwise be permitted.