Amorim was let go following an explosive attack on the United hierarchy, less than 24 hours after another poor performance in the draw with Leeds United.
Ex-United midfielder Darren Fletcher, who is currently the coach of their under-18s, will take charge of their next Premier League match against Burnley on Wednesday night.
Messages of support
Before United take on Burnley, several stars have sent messages of support to Amorim as they patiently await to see who could fill his shoes in what will be a caretaker role.
United captain Bruno Fernandes said: "Thank you Mister. Wish you and your technical staff all the best."
Joshua Zirkzee: "All the best for the future boss."
Patrick Dorgu: "Thanks for everything Mister. All the best in the future."
Matthijs de Ligt: "Thank you for everything boss. Good luck for the future." A message which was repeated by Harry Maguire.
Benjamin Sesko: "Thank you for everything boss."
Amad Diallo: "Good luck coach, thanks for everything. I wish you the best."
England international Mason Mount also posted: "Thank you, gaffer. All the best to you and your staff for the future."
Chido Obi: ‘Thanks for everything, gaffer, especially for allowing me to make my debut for such a big club. Wish you all the best.’
Finally, Harry Maguire posted: "Thank you for everything, boss. I wish you all the best in the future."
The post-Amorim era begins on Wednesday night as United aim to pick up 3 points and move into the top four above Chelsea and Liverpool.