Amorim is set to give both summer signings a full debut against the Gunners at Old Trafford.
Asked how he felt ahead of kickoff, the manager said, "Confident. I know that we are going to struggle in some moments. It’s a game against Arsenal, so we will struggle in some moments.
"We are more prepared, and I think, again, I feel that we have more players that can help us, in one moment, to change the momentum of the game and that can give you confidence. And we have more options if things are not working well, we can change things. So that gives me more confidence for every game.
"It’s that feeling that we could struggle here or there, in the way we play, but we can score. I think Cunha can – and you saw it last two seasons – catch the ball, and he create something, Bryan can make one run and he’s there to score a goal. These kinds of things can help us a lot, especially in moments that we are struggling, one guy can change the momentum of the game in the stadium."
Amorim added, "We prepared well during the pre-season.
"Pre-season is pre-season. We are going to start, we are going to struggle, but what we are going to see on Sunday, then we are going to work to improve, then we are going to improve during the season, but we are prepared to win against Arsenal.
"That is the only thing that matters."