Please Wait . . .
Neither has made the expected impact in English football, with those at Old Trafford and Stamford Bridge still waiting on a spark.
Van de Beek can put his lack of progress down to limited game time, with Ole Gunnar Solskjaer continuing to favour other options as transfer talk around the Dutchman starts to circulate once again.
Havertz, meanwhile, has had to overcome a bout of coronavirus in west London, with the 21-year-old still looking to adjust to new surroundings and a different system as a result.
Bosz, who has worked with both men during his coaching career, believes questionable calls have been made on the part of heavyweight outfits as they struggle to find value for money.
He told The Athletic: “Some players take more time than others, in all leagues. But I do question why Manchester United brought Donny in.
“They already have the best player in the league in that position: Bruno Fernandes.There is no space in their midfield for another number 10.
“Donny can play as a number six, but it must be a compact pitch. If it becomes a big pitch, it’s not his game.
“As for Kai, I can see why Chelsea brought him inbut I cannot yet see the exact idea Frank Lampard has for him.
“It’s really good that he protects him in the press, though. But in the end, you must deliver, you must score goals and make goals. For a €100 million transfer you must play, and he isn’t.”
While Van de Beek and Havertz are still searching for a spark, another player that Bosz is familiar with from his time at Ajax, highly-rated winger Hakim Ziyech, has been catching the eye at Chelsea.
Pressed on why the Morocco international is succeeding where others have failed, Bosz added: “Kai plays the piano, but Hakim is from the streets.