Garnacho came off the bench to change the tie as he laid on Josh Zirkzee's equaliser before Harry Maguire headed home the winner in injury-time.
Speaking after the 2-1 win, Amorim said of the winger: "We want players like Garnacho, who is really important. He changed the game today, with the runs behind. Of course, you can feel it, that the opponent was getting tired adjusting with a lot of difficulties, not in the first half, but in the second half to stop Garnacho in the one-against-one, so we are very happy with him. And I think he helped a lot to change the game today.
“He doesn't need a big change. We are talking about like the standards. It's just to train well, to receive the information, to understand that we want to help them. We want to play in the different system. But it's not complicated. So, he changed everything.
"He trains really well. He stayed on the bench like five games in a row. Every time he came on the pitch, it was a different guy, receiving the information and playing. So it’s simple things, it’s not a big thing. It's just, I’m really happy and you can see it. I think he’s improving.”