Big changes are underway at United. Changes that could see some established favourites fall by the wayside. If Amorim is good to his word. If he does intend to demand instant adjustment to his favoured system. Then it's difficult to see where United's raft of fullbacks fit in his plans.
The Portuguese has arrived championing his 'three at the back' formation. And to be fair, it is a genuine three centre-back defence. It's not a back five. It's not a formation which fills the wide positions with defensive-minded fullbacks masquerading as wingers. It's a real, helter-skelter back three, with those roles on either flank filled by out-and-out attacking wingers.
"I think you will see an idea," Amorim stated last week, when pushed about how he wants the team to play. "You could like it or not, I don't know, but you will see an idea.
"You will see a positioning. You will see something that we want to reach that kind of level. You will feel that.
"We have to know that it's like two trainings before the first match. This is the best league in the world. But if I have to say something to you, you will see an idea. This I can guarantee."
Indeed, for that Sporting team that played Manchester City off the Alvalade pitch, think Marcus Rashford for Maxi Araujo. And Alejandro Garnacho for young Geovany Quenda. Amorim will demand aggression, pace and real one-on-one ability from his wide players. Again, to be fair to the new manager, all in the best traditions of the United Way. He wants flair, pace and trickery from his wingers. But there's a qualifier. For the likes of Rashford, there'll be demands like never before on their work off the ball.
Amorim again, "A lot of people now talk about the 3-4-3 and the 4-3-3 and all that stuff. But when I think as a player or as a team-mate of Manchester United, it is not a system or formation – it's like the character of the players, the way they see the club.
"So we have to focus on that before everything of how we play, how we press. The most important thing for me, at this moment, is to create the principles, the identity and the character that we had in the past.
"Of course, we are going to prepare for the games, but we will focus a lot in our game model."
Bold. Exciting. If it all comes together for Amorim, United could truly return to those rip-roaring days of Sir Alex. He may be steadfast on his formation and what he expects from those inside his playing system. But this isn't the paint-by-numbers stuff of Louis van Gaal. His commitment to the type of player he wants in those wide positions is proof enough of that. The question is, whether Rashford and co have it in them to meet the new manager's demands?
In the meantime, there'll be a number of senior players at United wondering what's next? Shaw. Malacia. Even Diogo Dalot and Noussair Mazraoui. None of them can be compared in style to Araujo and Quenda. That's not to say Amorim hasn't played recognised fullbacks in those wide roles. But it's clear, given the options, as he did on the biggest stage against City, he'll back himself and his attacking players if the opportunity is there.
And it'll be something never before seen - at least consistently - from a United team. It'll boast the spirit; the excitement; of Sir Alex's teams. But even Fergie didn't have the bottle to play a formation as attacking as this.
“We did in the early years when we struggled," former United defender Gary Pallister recalled to Tribalfootball.com last week, "I think we tried Robbo (Bryan Robson) there who played as a sweeper for a couple of games.
“I actually think we had Paul Ince play sweeper for a couple of games so we did toy with the idea. I think in the early days when it was a bit of a struggle in that 1989-90 season, we did play it a few times as it was something we fell back on as we were conceding to many goals.
“I have no issues with a back five because it can be quite attacking depending on your wing-backs and how they play."
And that's just it, as Pallister points out, under Fergie United played the three centre-halves with fullbacks in the wide roles. It was a pure, pure back five. But Amorim's system isn't built for that. It isn't built to be safe. If he can get it altogether, it'll be a pure back three and wingers where Fergie had his fullbacks. Again, it'll be something not ever seen consistently at United.
Where that leaves the squad's current fullbacks, only Amorim can tell us. But if he gets it right, it can be exciting times ahead for United fans.