Garnacho was bright in a rollercoaster first half but was the player sacrificed after Patrick Dorgu was shown a straight red card and Manchester United were reduced to 10 men.
He was replaced by Noussair Mazraoui on the stroke of half-time, a decision which large sections of the home crowd audibly booed, before trudging straight down the tunnel back to the dressing room.
After the match and moments before Amorim faced the media in his press conference, Garnacho posted on his Instagram story a picture of him walking down the touchline towards the tunnel without a caption.
‘You are making a connection with [Marcus] Rashford, right? I know, I know,’ Amorim said in response to a suggestion about Garnacho’s attitude.
‘What I’m saying is I’m going to talk obviously with Garnacho about that [going down the tunnel]. So I will talk about that if you want in the next press conference.’
Alejandro Garnacho was taken off in the first half after Man United were reduced to 10 men.
Pressed on why he chose to sacrifice Garnacho given he looked to be the only attacking threat for United, Amorim added: ‘The thinking was we were playing more in the 5-3-1 and I know that is a risk.
‘I felt the team was OK in controlling of the game and then you make the substitution and you have to choose someone to come out. It was my choice.’
Garnacho got on the wrong side of Amorim earlier in the season away to Viktoria Plzen in the Europa League.
In a story exclusively revealed by Mail Sport, Garnacho was axed from the Manchester United squad over a show of dissent towards Amorim.
