Olosunde arrived from New York Red Bulls last year and Mancunian Mitchell is on the shortlist for the Reserves’ Player of the Year award.
They were also accompanied by Matty Willock and Scott McTominay, who were also on the bench for draws against West Bromwich Albion and Swansea City last month.
The Portuguese boss confirmed he could be set to rest key players against Arsenal and only hinted it could be some players who played too many minutes in April as there are some important fixtures coming up.
Confirmed United squad members:
David de Gea, Sergio Romero, Joel Pereira, Matteo Darmian, Matthew Olosunde, Chris Smalling, Eric Bailly, Axel Tuanzebe, Phil Jones, Daley Blind, Demetri Mitchell, Michael Carrick, Scott McTominay, Matty Willock, Paul Pogba, Ander Herrera, Jesse Lingard, Henrikh Mkhitaryan, Juan Mata, Marcus Rashford, Wayne Rooney and Anthony Martial.
The side will still play for the victory, but it’s clear the attention has shifted to where Mourinho believes United have the best chance of achieving Champions League football.