Amorin has left Rashford out of his squad for the past three games, which has seen the striker publicly declare he wants a "new challenge".
Ahead of their visit to Wolves on Thursday, Amorim said of Rashford: “Some guys have a big responsibility here because they have been here for a long time.
“If you have big talents, we need big performance, big responsibility, big engagement to push everybody forward in this moment.
“This is maybe one of the lowest moments in our club. We have to face it and be strong.”
On solving the club's issues, he added: “If I knew, I would solve all the problems of this club, even this.
“I know what I am going to do. That is so clear for me. I will not say I am feel relaxed because I’m really frustrated. It’s a very difficult moment but we will solve problems step by step and find answers for everything.”