The 21-year-old started just 16 games in Amorim’s troubled 14-month tenure at Man United but has since rediscovered his place under Michael Carrick and has signed a new contract.
Amorim’s inability to find Mainoo a place in his heavily criticised 3-4-2-1 system sparked concerns that United could lose one of their most talented academy products in years.
Speaking to Sky Sports, Mainoo admitted he considered his future with Amorim in charge, but becoming a United regular was always his priority.
"When you're not playing many games, or any games, you consider all things,” he said.
"But at the forefront of my mind was always to play for Manchester United and continue to play for this club that I've grown up at.
When asked if he felt Amorim left him out because he did not see him as a fit for his system, Mainoo responded: "Yeah, when there's new managers, they have their way that they want to play and if they think you don't fit that, then you don't fit that.
"All I can do is try and work and train to maybe see it in a different light."