The United boss felt his side had control for long periods but struggled to convert chances into goals.
Amorim urged his players to be more ruthless in front of goal as they look to bounce back in their next fixture.
He stated post-game: "It was the biggest difference of the game, they (Tottenham) scored and we didn't. We had the opportunities to score, then in the first half we pushed a little bit harder. We suffered in some transitions trying to get a result, but in the end they scored and we didn’t.
“We need to put the ball in the net because we had some chances, we created some chances which is the hardest part. In some games we are there near the box but we don’t create chances. Today we created the chances but we need to score to win games.”
And adding on player absences, he stated: "You start with one idea. We were asking about a long week for so long. And we worked our principles but day after day, you lose players that change your approach to the game. I could not play the same way with Joshua (Zirkzee) as I can with Amad. Sometimes you want Bruno (Fernandes) to reach the ball in the build-up because he's really good switching the play. But then you want Bruno also to press and it's really hard. And when you are changing all the time to get the players to react to the base, it's really hard.
"4-4-2 in the low block is harder to play against this team than what we did today, that's my opinion. They are so open and stretch the team. What you see guys and what you discuss every week, I also see. I have a lot of problems, my job is so, so hard here. But I stick with my beliefs."