Rashford and Garnacho were left out of the Man United squad for Sunday's Manchester derby against Manchester City, with Amorim confirming ahead of the match that the pair were not injured.
There had been talk of potential disciplinary issues involving both players, but Man United's head coach insisted that was not the case, and he said that "next week" is a "new life", with the pair in with a chance of returning for the trip to the Tottenham Hotspur Stadium in the quarter-finals of the EFL Cup.
"It's important to say why: was not a disciplinary thing," Amorim said during his post-match press conference. "Next week, next game, new life, they are fighting for their places.
"But for me, it's important: the performance in training, the performance in game, the way you dress, the way you eat, the way you engage with teammates, the way you push your teammates, everything is important in our context in the beginning of something when when we want to change a lot of things.
Rashford, Garnacho could return to Man United squad vs. Tottenham
"When people in our club are losing their jobs we have to put the standards really high and for that they have to fight for a place in the team. And today the team proved we can leave anyone out of the squad and manage to win if you play together.
"I'm going to say again was not a disciplinary thing. It's the small details. You can see the games like I see, there are some things that have to change.
"But it is a new life, it's not a disciplinary thing, it's the performance in training, the performance in game and I have to choose players. Jonny Evans did everything right, he was at home, and he is really important for us.
"If it was disciplinary, I would say that here and it will be a bigger problem but was not that. Sometimes I want to improve my players and you understand that for so long.
"We tried for example with Rash, it does not work. Let's continue to do the same thing or try something different? So it's as simple as that. If they train well with the talent they have we will be so much better with them.
"But they have to work hard, they do, today they trained really hard. New week, new life, let's see. You can dress in a way that I don't like, really don't like, but it's not a disciplinary thing. It's the small details. But the performance in training and games, then I have to choose. That's it. New week, new life. That's it."
How did Man United perform without the duo against Man City?
Mason Mount and Amad Diallo were selected as the number 10s behind Rasmus Hojlund in the Manchester derby, but the former had to be replaced in the early stages of the contest due to an injury problem.
That led to Bruno Fernandes moving into the number 10 spot, with Kobbie Mainoo being introduced in midfield.
Amorim's side trailed to a Josko Gvardiol header at the Etihad Stadium, but Fernandes levelled the scores from the penalty spot in the 88th minute before Amad won it two minutes later with an excellent finish.
Antony and Joshua Zirkzee were the attacking options in reserve against Man City, and Amorim now has a major decision to make ahead of the Spurs match, as Rashford and Garnacho could be valuable options off the bench, but their involvement in that contest will depend on how they respond to the disappointment of being snubbed for the derby.
Written by
Matt Law