Butt insists Amorim doesn't have the players to successfully play his 5-3-2 system.
He told ‘The Good the Bad and the Football’ podcast: “Forget the system for a minute, the players are not at the level they need to be, not quick enough, not aggressive enough.
“The two lads in midfield, Bruno Fernandes and Manuel Ugarte, they’ve not got the legs to do it in a three, let alone a two
“If he wants to get results and keep his job in the long run, he is going to have to bite the bullet and change a bit – otherwise they’ll keep losing games.
“You look at Pep Guardiola he’s got a philosophy that is the best anyone football has ever seen, even as a United fan. But even he changes.
“So he brought Jeremy Doku off the left and put him in the middle – because everyone knows how United will play.”