Those results mean United were one of three top-flight clubs to post a 100 per cent record in October, alongside Arsenal and Aston Villa.
That also sees Mikel Arteta and Unai Emery nominated for the prize alongside Amorim, and Andoni Iraola of Bournemouth, whose team won two and were unbeaten across the month.
The vote is now open and you have until it closes at 12:00 GMT on Monday 3 November to get behind Ruben with your selection. The winner will be named at 12:00 GMT on Friday 7 November.
Earlier today, it was announced that Bryan Mbeumo features on the shortlist for the Player of the Month. You can vote for Bryan here.
