As expected, United fielded a completely different XI in the second half, with Sergio Romero, Matteo Darmian, Valencia, Chris Smalling, Eric Bailly, Andreas Pereira, Ander Herrera, Marouane Fellaini, Juan Mata, Anthony Martial and Marcus Rashford introduced.
The second 45 minutes was not as free-flowing and gave Mourinho headaches more than anything else.
First, Mata hobbled off the ground due to a leg injury after signalling to the bench before the hour-mark – replaced by Demetri Mitchel.
Valencia was then bizarrely sent off for a late tackle from behind on Sebastian Saucedo. The referee initially awarded a foul and spoke to the United full-back before brandishing a red card.
Despite their numerical disadvantage, United should have sealed the win in the 78th minute, but Smalling headed over the crossbar with an empty net at his mercy.