Bruno Fernandes struck late to keep United's hopes of reaching the Europa League's round of 16 alive.
Amorim said afterwards: "We did well. We played better with the ball. I think we started well and then we lost control of the game because of some bad decisions but the lads did well. We are so near the second goal with so many chances, it's so hard but they recover.
"We are not playing our best but we regrouped from the last game. I know the opponent is different. It wasn't as fast. You can see the connections. I think we need to be more clinical in the right moments because that can help us a lot."
On finishing in top eight, he added: "It's two weeks free to prepare for the Premier League so it's really important to stay in this position.
On Matthijs De Ligt's injury: "He felt something in his leg. Also, Leny (Yoro) so we cannot risk anything. We have to win but we have to protect the players and show that everyone matters in this moment.
"We started the game scoring first, that is important. You can see that in Europe, it is quite different. We scored the first one and in the Premier League, it is not a foul."