Mourinho recalled Alexis Sanchez, who hadn't even made the bench for Saturday's defeat, among four changes from the weekend.
After finishing second in the Premier League last season, United are now 10th in the table after seven games, already nine points off league leaders Manchester City.
At yesterday's Champions League media conference, Mourinho was asked about the Chile global after he was dropped for defeat to West Ham.
Scholes hailed Rashford's effort and performance in a game which couldn't ease the pressure on United in a tough time for the Reds.
If they fail to win either of those, United could face a final-game trip to Valencia needing a result to qualify.
The atmosphere at Old Trafford was rather flat as United lacked any bite in a contest played at walking pace, with the visitors content to keep them at bay with crisp one-touch passing.
Mourinho might not have been aware of the traffic problems that have become a regular pain for Mancunians, but he did joke recently that it takes two hours to get between Old Trafford and the Lowry Hotel, the team hotel where he has lived for the past two years.
Minor details are important. Valencia have one point and Young Boys none. He gives United more penetration than others players and a higher intensity.
Mourinho needs more players like Rashford and Shaw in his starting XI.