Amorim made six changes to his starting side for Wednesday's Premier League clash against Arsenal despite the Red Devils putting in their best performance of the campaign against Everton on Sunday to recored a 4-0 win.
Lisandro Martinez and Kobbie Mainoo both missed out through suspension, but Casemiro, Amad Diallo, Marcus Rashford and Joshua Zirkzee were rotated out of the side.
Man United suffered a 2-0 defeat at the Emirates Stadium, with Arsenal scoring from two set pieces, and Amorim has admitted that rotation will be the name of the game in the coming weeks.
"In this moment, it is impossible to play with the same team. They [the players] have to feel they are part of the team, but we are changing the methodology, we are changing a lot of things," Amorim told reporters after the match.
Amorim explains Man United rotation after loss at Arsenal
"We are changing the way we play, the way we press, so we have to have all the players fit. We cannot have injuries in this moment because it will be tough to cope with all the games so we will manage the way we feel is the better way for the team.
"It's not that I like to change [the line-up] all the time but if you see the game, Mason Mount cannot do the full game because we have to be careful in this stage.
"Harry Maguire has to leave the pitch no matter what. Leny Yoro, we have to control the time he plays. We did the same with Luke Shaw, we did the same with Ty [Tyrell] Malacia. We have to control the time, manage a new idea, win games and try to maintain all the players' fitness. It's a difficult period but let's focus on the performance and then think about the next game."
Arsenal scored from two of their 13 corners on Wednesday, and Amorim has conceded that his side struggled to deal with the set-piece threat from the North London outfit.
"We already knew that it would be a tough game. I think the corners changed the game, the set-pieces. Then we lost the momentum, we tried everything then to control the game again. You feel it in the first half, in the environment of the stadium, that we were causing problems. We need to improve in a lot of areas of our game, but we were controlling the game," he added.
"They are very good because they have a lot of time working on that. Especially on that, they have big players for that, so it is a strategy, and we had two weeks to work on that. We tried to do it but we know every team in the Premier League is suffering with set-pieces. It was a shame because we were not playing very well but also Arsenal was not playing very well.
"You learn all the time, it's not a good thing or a good feeling, it's really hard. But you have to take the positives and the negatives like in ever other game. So, let's focus on everything we are doing, recover all the players to be fresh on the next game and go again. Full stadium with our fans and we are going to succeed. We need a little bit of time."
What next for Man United?
Man United will be aiming to bounce back from their first defeat since Erik ten Hag's departure when they welcome Nottingham Forest to Old Trafford in the Premier League on Saturday evening.
Martinez and Mainoo will be back in contention after serving one-game suspensions, while Amad, Rashford, Casemiro and Leny Yoro will be in the manager's thinking when it comes to spots in the side against the two-time European champions.
Written by
Matt Law