Maguire featured for United in a new three-man defence as his side conceded a late goal against Liverpool on Sunday evening, drawing 1-1.
The England international has made an assured start to his United career, but former Tottenham Hotspur and Real Madrid player Van der Vaart has insisted that Maguire was not worth his hefty £80m transfer fee.
“When I watch an amateur game on Sunday, I find three players playing like him. I’m serious,” Van der Vaart said on Ziggo Sport.
“It may sound silly, but he will not hear it anyway. After all, we’re talking about a €90 million transfer here. Then [Virgil] van Dijk is worth €300 million.”
Van der Vaart previously slammed Maguire as “the worst player on the pitch” when England were beaten 3-1 by Holland in the Uefa Nations League semi-finals in June.
“It’s funny because during the Nations League, I was doing work for Dutch television,” he recently told Sky Sports.
“And I remember we were saying ‘Harry Maguire was by far the worst player on the pitch’.
“And then two months later, £80-£90m? Unbelievable.”