Amorim has failed to turn around the club’s fortunes since replacing Ten Hag back in November 2024, winning just six of his 25 Premier League games.
Despite their dire domestic form, United may still qualify for next season’s Champions League as they face fellow strugglers Tottenham in the Europa League final.
Van der Gaag, who followed Ten Hag from Ajax to Man United back in 2022, has admitted he has some sympathy for the man who replaced his friend.
"A coach always needs victories to get his ideas across and for the players to believe in him," he told A Bola.
"Coming in mid-season is always difficult, and even more so with the changes that are happening, especially outside the club. In the structure, training centre, stadium, and there are people who can't stay at the club and will be fired.
“There's a lot going on around the club. Then a top coach arrives here in Portugal, but he's faced with this reality, he has no control over it and he needs to work. It's not easy and I hope he has time to change because it's not easy."