Ajax coach Erik ten Hag is baffled by Donny van de Beek's struggles at Manchester United.
Van de Beek is in his second season at United after his departure from Ajax.
Ten Hag told De Telegraaf: "Donny's situation is difficult to understand.
"If you do not get chances to play, your development will stop, it's that simple. I have been in contact with him from time to time and try to encourage him."
Van de Beek was a late substitute in United's win against Crystal Palace on Sunday, marking the debut for new manager Ralf Rangnick.