The 20-year-old academy product has played just 191 Premier League minutes under Amorim, mostly off the bench, due to overlap with captain Bruno Fernandes.
Amorim rates Mainoo highly but prioritizes training and match performance, shrugging off critiques from Paul Scholes, Gary Neville, Roy Keane, and Nicky Butt by noting he'd face no backlash if winning.
He's open to a January loan discussion if Mainoo initiates it, while highlighting chances given to other prospects like Toby Collyer, Harry Amass, and Chido Obi-Martin. With United around 13th, Amorim admits he's not doing his job well enough yet.