Manchester United could be without up to six first-team players against Nottingham Forest on Tuesday.
Diogo Dalot, Harry Maguire, Raphael Varane, Jadon Sancho and Axel Tuanzebe all nursing injuries and Lisandro Martinez likely to be unavailable after Argentina's World Cup win.
Ten Hag admitted that it is too early to determine whether Martinez, who won the World Cup with Argentina, will be available for the game.
While Dalot is also a doubt after sustaining a hamstring strain in Portugal's quarter-final defeat to Morocco.
"Centre-back Maguire is currently ill and will have to be assessed late. "Harry is sick, and I do not know how that will develop," Ten Hag said.
"We have to wait and see if he will be available for Nottingham Forest [on Tuesday]."
Varane is yet to return from international duty, and Sancho is not expected to be available as he is yet to return to squad training.
Although Tuanzebe was spotted back at Carrighton this week for the first time since July, he is still building up fitness before returning to group sessions. United and Forest advanced to quarterfinals of the Carabao Cup with wins over Burnley and Blackburn respectively.
