After suffering an unexplained injury in early November, the Red Devils placed Sancho, 22, on an individual training regimen during the World Cup break.
Ten Hag had to leave the player at home for United’s training camp in Spain.
And the manager has revealed that he does not yet have a return date for Sancho in mind.
“[Sancho] isn’t in good enough shape to be here,” he told reporters at the team’s Spanish training camp. “First and foremost, we did not see him in United’s last two games.
“So he wasn’t in the appropriate condition, in the right fitness level, so now he’s on an individual course and we want him to finish that program and hopefully, we see him back soon.
“We want to get him back as soon as possible, but I can’t say when that will be.”