Manchester United named Wayne Rooney on the bench, but started with the handicap of Marouane Fellaini in midfield.
United kept the score goalless in the first half, and Marcus Rashford put United ahead with a deft finish towards the start of the second period.
Marouane Fellaini doubled United's lead when the ball was hit at him, and bounced over the line off him from a couple of yards out.
Fellaini was at fault when he failed to header James Tomkins' goal from Andy Carroll's knockdown, and Louis van Gaal also made sure of making his pointless full-back substitution by replacing Marcos Rojo with Antonio Valencia.
United were hampered by an injury to Ander Herrera, who may have potentially seriously injured his foot.
Rashford was replaced by Rooney in the last minute of normal time. United were under sustained pressure for four minutes of added time,