Duo Rhys Bennett and Kobbie Mainoo are now both academy graduates and will remain as part of the United squad for the rest of the season.
Erik ten Hag took his squad to Spain during the World Cup for a warm-weather training camp and have played out two friendly losses to Cadiz and Real Betis.
Bennett, 18, captained United's youth team to the FA Youth Cup last season with Mainoo, 17, who was also part of that cup-winning side.
Neither has made their competitive debut for the senior side, but Mainoo was an unused substitute against Newcastle United earlier in the season, and both players will be eyeing up United's EFL fourth round tie against Burnley as a chance to make an appearance.
The Red Devils return to action in the EFL Cup at home against Championship side Burnley on December 21 before then welcoming Nottingham Forest at home on December 27 in the league.
United will look to climb the Premier League tableas they currently sit in fifth place, just three points off fourth-placed Tottenham Hotspur with a game in hand.