Januzaj joined Dortmund on loan from United in August, but had his season-long stint cut short by mutual consent after he failed to make a single start in the Bundesliga.
After the 20-year-old returned to Old Trafford, Dortmund boss Tuchel revealed how unimpressed he was with the player’s application.
"It is a pity he did not show the desire and attitude you need to progress at his age," the BVB boss said to Sportbild.
Van Gaal on Januzaj: I said he would struggle to play at Dortmund, and I was right
"My feeling was that he never was completely with us, that a part of him always stayed in Manchester and he compared everything here with United.
"We were not able to help him to shake that off."
Manchester United's Adnan Januzaj during the Press Conference
Image credit: Reuters
Van Gaal has told Januzaj that he must prove himself with United’s U21s for the time being and insisted that he warned the player that a loan move to Dortmund would never prove to be a good idea.
"I hope he can show his talent this year for Manchester United," said Van Gaal.
"I believe in the talent of Adnan Januzaj. I have said this previously. I also previewed that it shall be very difficult to play matches in Dortmund and, unfortunately, I was right.
“Then I think that, if he cannot play there, then he would be better training with us here to show his talent in the first team."
This is a damning assessment from Tuchel and it will not do Januzaj's prospects at Old Trafford - or indeed elsewhere - any good in the short term. It is now up to Januzaj to prove the Dortmund coach wrong and finally establish himself as a first-team regular under Van Gaal - something which his talent suggests he should be able to do with the right attitude and approach to training. It really is up to him now.
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