Erik ten Hag’s side will play Cadiz and Real Betis next week as they step up their preparations for the second half of the season.
But Sancho does not appear likely to play a part in either fixture as he will train away from the first-team squad.
Last month, Sancho was spotted training with Dutch amateur side OJC Rosmalen after he was recommended specific coaches to work with by Ten Hag.
The 22-year-old missed United last four matches before the World Cup break due to illness but was expected to be part of the squad which travelled to Spain.
However, a statement from United on Sunday morning read: ‘Jadon Sancho is continuing his individual training programme as part of a process to get back to his highest level. The club is fully supporting him in this.’
Axel Tuanzebe is also not included in the squad as he continues to recover from injury.
Meanwhile, Aaron Wan-Bissaka and Brandon Williams are both included in United’s squad.
MAN UTD SQUAD FOR SPAIN TRAINING CAMP
Goalkeepers: De Gea, Heaton, Bishop, Dubravka.
Defenders: Lindelof, Wan-Bissaka, Williams, Mengi, Bernard, Jurado, Hardley, Bennett, Oyedele, Murray, Fredricson.
Midfielders: Van de Beek, McTominay, Savage, Iqbal, Hansen, Gore, Mainoo.
Forwards: Martial, Elanga, Shoretire, Garnacho, Hugill, McNeill, Emeran.
United’s domestic season resumes on December 21 as they play Burnley in the Carabao Cup.
Ten Hag’s side will then resume their Premier League campaign on December 27 against Nottingham Forest.
For more stories like this, check our sport page.