Manchester United received a triple boost at training on Monday with Sergio Reguilon among those featuring after injury.
The Spanish left-back has only managed to start two games since joining on loan from Tottenham late in the summer transfer window, and sat out the weekend win at Sheffield United due to illness.
And he featured in training ahead of Tuesday's Champions League visit of Copenhagen.
Ten Hag told reporters: "Sergio was fit [on Friday], trained all last week and yesterday he was part of training and today he will train and we have to assess if he is ready and game fit and can be involved in the squad.
"We have to see if he is fit enough to be available."
Casemiro was also part of the session at Carrington but is suspended for the European fixture.
United opted to allow the midfielder to miss win at the Blades to give more time to recover from a knock picked up on Brazil duty, even though he had already made his playing return with his country.
Tyrell Malacia also featured in an individual training session as he continues to come back from an unspecified injury he suffered in the summer.
Yet to play this campaign, the Dutchman is expected to still be a few weeks away from playing having missed pre-season.
United welcome Copenhagen to Old Trafford on Tuesday ahead of the derby with Manchester City five days later.
Aaron Wan-Bissaka, Kobbie Mainoo and Luke Shaw are among the senior players who remain on the treatment table.
