Jose Mourinho made eight changes to his starting line-up for the first game of the Europa League group stages but oversaw a comfortable win.
After a sluggish start, Leicester City clicked into gear to comfortably defeat Zorya Luhansk in their opening Europa League fixture.
James Tavernier scored his ninth goal in 10 outings before Kemar Roofe sealed victory in style for Rangers in Belgium.
Arsenal have captain Pierre-Emerick Aubameyang to thank for a 2-1 win at Rapid Vienna, who had taken the lead after a Bernd Leno mistake.
Mesut Ozil's future and Thomas Partey's arrival were among the topics discussed by Mikel Arteta ahead of Arsenal's trip to Manchester City.
Manchester United dominated Copenhagen in the last eight of the Europa League but needed an extra-time penalty to advance.