The young Argentina international was taken off against Ipswich Town at Old Trafford just before half-time, for tactical reasons, after Patrick Chinazaekpere Dorgu was shown a straight red card.
On a night of heavy Manchester rain, Garnacho walked straight to the dressing room following his departure and, in the post-match interviews, Ruben confirmed he would speak to the player about that decision.
As Amorim explained during his press conference on Friday afternoon, all has been made clear with the player and, amusingly, the head coach revealed Garnacho has a small punishment to pay.
“Yeah, he came to me,” Ruben told reporters when asked.