The 27-year-old England international missed his third consecutive match on Sunday as United suffered a 3-0 defeat at home to Bournemouth.
Rashford was also left out of the squad for the derby victory against Manchester City earlier this month, as well as for Thursday’s League Cup quarter-final loss to Tottenham.
Just two days prior to the defeat against Spurs, Rashford expressed in an interview that he was “ready for a new challenge and the next steps” in a career that began in the United academy.
“It is a hard situation but I understand that this kind of player have a lot of people around them, and making some choices that sometimes is not the first idea from the player,” Amorim told Sky Sports on Monday.
“They chose to do that interview because it’s not just Marcus. I understand that so for me as a coach I’m just focused on the performance, the way he trains.
“The rest, I think, is better for me and the club to deal with that when the times comes.”
Amorim also expressed his support for Rashford, who is under contract until 2028 and is keen for the player to stay at United.
The Portuguese said he can “separate” his relationship with Rashford from the decisions of the people advising him.
“At the moment I’m just focused on improving Marcus,” added Amorim.
“We need a lot in this moment, (from a) talented guy like Marcus, and I forget for now the interview. I just see what I see on the pitch.”
Manchester United's defeat against Bournemouth has resulted in their 13th-place standing in the Premier League, their lowest Christmas ranking in the top flight since 1986.
Amorim's team will resume play against Wolves on Boxing Day, followed by a home match against Newcastle the following Monday.