The midfielder has struggled for minutes so far this season, with Amorim admitting a lack of European football has created issues for his deep squad.
"We need to go to Europe, because of everything," he said. "Imagine for me to have Kobbie Mainoo with the minutes that he's playing, he needs more games for me to make a rotation.
"Because with one game it's really hard. I have to take out one of the guys that is playing to put in another. When you have more games, you can divide, you can manage the group in a different way."
Amorim admits he hopes players like Mainoo can draw some inspiration from Casemiro.
"First of all, they understand, I prove that anyone can play, and everyone has to do the same things," he added. "Not in the same way, but there are some things that everyone, no matter what is your name, you have to do it to play for Manchester United.
"I try to explain all the time to the players that we are not just playing today, not just this year, but then the next seasons. So they feel that they are part of the journey, and that we are part of something bigger than just one game or one season. So they are part of our path.
"Then I show also to them that Casemiro was not part of the starting 11. He was behind and then he fought. He won the place, and if you win the place, you will be playing.
"So I think that helped them to understand that I'm trying to be fair, and they are part of something very special that is very important to us."