Amorim’s side earned a much-needed Premier League win over newly promoted Sunderland at Old Trafford on Saturday.
Mason Mount scored the opener before striker Benjamin Sesko secured all three points with a tap-in on the 31st-minute mark.
Speaking to BBC Sport after the game, Amorim praised his side’s ability to earn the win with a relatively comfortable performance.
He said: "That is the kind of game where when we're not playing well, we're defending well. We had our moments; we were focused and competitive.
“Not the perfect performance. Senne (Lammens) did really well. We were a competitive and adult team today. We need to win these games with a clean sheet. Good for us."
Read more: Sesko scores as Man Utd grab much-needed win
"We need to understand that we need everyone to be ready to play. It's a long season, we have a lot of problems, anything can happen.
“The important thing is that the teammates helped Lammens a lot to have a very good performance."