Van Halst, once of Ajax, said on Ziggo Sport: "I would be really worried.
"Last season (manager Ole Gunner) Solskjaer always played with Fred and (Scott) McTominay and he is now putting them up again. Van de Beek is just sitting there.
"He doesn't even come in. He's on the couch for ninety minutes."
Former Holland striker Youri Mulder also remarked: "It is very bad for such a boy to only play six or seven times in a year. That is bad for your rhythm. You can earn a lot more, but you also have to see where you can play."