Amorim is under scrutiny having only won one of United’s first four games of the season and also been knocked out of the Carabao Cup in the second round by Grimsby Town.
Addressing newsmen ahead of a must win game with the London side, the Portuguese acknowledged pressures over the club.
He said: “This is football and this is the club with more pressure, maybe, than any in the world, but we want to win.
“Last year I was very critical of the way we played. I think we are playing well until the boxes, defending and attacking.
“We need to be more aggressive in the boxes. We need to be more clinical. The rest I think we are improving compared to last year. We are in a better place.
“But we need to win. We lost against Arsenal and Man City. Here, losing, especially in the beginning after last season, is a problem.
“We need to be more clinical. The number of shots and the xG are good, but if you don’t score, it doesn’t matter.
“The way we suffered the goals, we can avoid that. We are being naive, we need to be more aggressive in order to win games.”