The 15-year-old formally requested to leave United last month as he asked for his youth registration to be cancelled, which would then allow him to leave the side.
Gabriel has not trained at Carrington since scoring a hat-trick on his UEFA Youth League debut against Sabah on September 10th, and he is not set to return anytime soon.
As per The Mirror and The Express, the teenager has been training in Barcelona with private coach Jack Hunter at the British School Stadium in Castelldefels.
This comes after he deleted all pictures on his Instagram profile relating to the Red Devils, in a stern message to the club.
Reports state Gabriel and his family are regular visitors to Barcelona and are keen to explore a move to the Camp Nou where they believe he would thrive at Barcelona.
Gabriel's family were concerned about his lack of game time within the United first team. This is despite him being just 15 years old.
Whether Barcelona can offer him a spot in the side is unknown, but with him being so young, it seems unlikely as he continues to develop.
Alongside Barcelona, Manchester City, Paris Saint-Germain, Real Madrid and Bayern Munich have been linked with Gabriel, who looks to be close to making his mind up.