The Portuguese dropped forwards Marcus Rashford and Alejandro Garnacho for "selection" reasons for Sunday's match at Manchester City and his gamble paid off with a dramatic 2-1 win, thanks to late goals from Bruno Fernandes and Amad Diallo.
Amorim has shown he is prepared to speak bluntly about the huge task facing him at a dysfunctional Old Trafford since he replaced the sacked Erik ten Hag last month.
Now he has shown he is prepared to walk the walk as well as talk the talk as he battles to force through a cultural and tactical reboot at the club, who are 13th in the Premier League table.
The former Sporting Lisbon boss has shown a willingness to rotate his men, unafraid to leave out big names.
But on Sunday Rashford and Garnacho - two of United's most potent attackers - were omitted from the squad entirely as Amorim showed his teeth.
Amorim said it was a "selection" issue ahead of the game at the Etihad, with both players training at United's training ground on Sunday morning.
Afterwards, he stressed it was not a disciplinary issue, though he did allude to the standards he expects.
"For me, what is important is the performance in training, the performance in-game, the way you dress, the way you eat, the way you engage with teammates and push teammates," he said.
"Everything is important in our context, the beginning of something when we want to change a lot of things when people in our club are losing their jobs.
"We have to put our standards really high, and for that they have to fight for their place in their team.
"Today we proved we can leave anybody out of the squad and you can manage to win if you play together."