Rasmus Hojlund scored a fine opener within 10 minutes of kick-off, and the Reds stitched together a number of pleasing moves throughout a keenly contested first 45.
Arsenal drew level through Gabriel Jesus and then edged ahead via Martinelli's aforementioned 81st-minute clincher, but the boss was reasonably satisfied with what he deemed a "good performance".
But what about our fans? There were 62,486 present in the SoFi Stadium in California, and millions more watching around the world.
At full-time, we asked them to nominate the United players that had impressed them in each half.