Amorim admits that Manchester United are seeking to add to the squad next month, though he insists any signing must be the right long-term fit.
He said: "We have space to have more players, but it is a very important thing in our club that we have a plan and we need to bring players that we know.
"It's hard to know for sure that everything is going to work, but we need to be certain of the players that we bring.
"If we are not sure, it's better not to bring anyone and to work with the players that we have. That is clear for me.
"Maybe I should be different like so many managers, but that is my thinking and I think it's the thinking of the board that we cannot do the same mistakes that we did in the past and we need to survive these moments because we have players coming from international (teams) and from Europe."