With the second-leg of their Europa League semifinal against Athletic Bilbao to come this week, Amorim selected a shadow XI, with Chido Obi, Tyler Fredricson and Harry Amass all starting.
Down 4-1 at one stage, United struck twice late on to offer some respectability to the scoreline.
Amorim insisted afterwards: "I liked (performance of) the young kids. I liked how we controlled the game without many occasions to score. In first 30 mins we struggle with set pieces but we already knew we didn't have the height to fight that.
"In second half we are near the draw and we suffer two goals like we did in beginning when we suffer one and let it go. We fight but in the end we lose but good things for the future."
On changes to his starting line-up, he also said: "We as a club we need to understand in this moment we have a big responsibility. We have to prepare a squad for different competitions."
On another Premier League defeat, Amorim added: "I think it's stressful to lose games. When we're fighting for a title it's not stressful."