The Danish striker, who was signed from Atalanta for a reported 72 million pounds, is struggling with a stress fracture of the back.

"As we said previously, he had a small issue and he's not on the levels where our players are in this moment so we have to train him," Ten Hag told reporters ahead of Monday's home clash against Wolverhampton Wanderers.

"Prognosis is always difficult to say. We are confident and we are positive."

The United manager said he was happy with the signing of Hojlund despite the club being linked with Harry Kane - who appears set to join Bundesliga heavyweights Bayern Munich.

"First of all, we have chosen a striker and we are really happy with our choice," the Dutchman said. "He's (Kane) a great striker... It's a miss for the Premier League, absolutely."

Defender Harry Maguire is likely to be available for United's Premier League opener, despite a reported deal being agreed with West Ham United for the out-of-favour defender.

When asked about Maguire's availability, Ten Hag said: "Of course (Maguire).

"(Tyrell) Malacia will take some time, same as Amad (Diallo) and Kobbie (Mainoo), they are impact injuries, all the others like (Dean) Henderson, (Rasmus) Hojlund, quite short notice, but it will take a few weeks," the Dutchman added, speaking about other injury problems within the squad.