Man United are not expected to welcome back any players from injury for the visit of Wolves on Monday.
Speaking on Rasmus Hojlund, Erik ten Hag said: "As we said previously, he had a small issue and he is not on the levels where our players are [at] in this moment.
"So now we have to train him. So the prognosis is difficult, always to say. We are confident and we are positive."
He added: "Some issues you mention from last season, like Malacia; he came to pre-season with an issue.
"We had 30 players on tour who were really fit and disappointment about Amad and disappointment about Kobbie [Mainoo], absolutely.
"But that's what happens when you go to the limits. Injuries are not avoidable but we have a strong squad and from there on we can pick a really strong team. And you see the two games last weekend of two teams, two strong sides.
"You go specific (about injuries): Malacia will take some time, same as Amad and Kobbie, they are impact injuries. All the others like Henderson, Hojlund, quite short notice but what is the definition of it, but it will take a few weeks."
Rasmus Hojlund is nursing a stress hotspot fracture of the back and is not match-fit yet while Dean Henderson could be rushed back into the squad as Tom Heaton has a calf strain that is likely to leave him sidelined for the rest of the month.
Tyrell Malacia missed the entirety of pre-season, Amad has a knee problem and Kobbie Mainoo is sidelined with an ankle injury.
