It was fast and furious at the Emirates Stadium as United raced into a 2-0 lead within 11 minutes through Antonio Valencia and Jesse Lingard.
Arsenal then utterly dominated proceedings with 75% possession and eventually made it 2-1 when Alexandre Lacazette fired past David de Gea.
But the Gunners' desperation was soon exposed when Lingard led a counter attack and found the back of the net for his second of the game.
Try as they might, Arsene Wenger's men were unable to recover - mostly because De Gea was an absolute rock in goal - and slumped to a 3-1 defeat.
There were talking points aplenty after the game, such as Paul Pogba's red card and Danny Welbeck's penalty shout, but there was another moment that somewhat slipped under the radar.
Four minutes after Lingard made it 3-1, Jose Mourinho replaced Anthony Martial with Ander Herrera to shore up the midfield.
It was a sensible call from United's manager, given they had a comfortable lead and were under a lot of pressure.
As you can probably imagine, though, Martial was absolutely livid, as you can see in the footage below.
Martial could be seen muttering under his breath as he walked off the pitch and football fans on Twitter think he was saying "puta" or "putain", which both translate to "b***h".
There are suggestions Martial's slur was actually directed at Mourinho, but there's simply no way of telling.
You could understand if it was given he was a threat against Arsenal, not to mention Mourinho's recent comments about why he's so inconsistent.
"I think he suffers a little bit with accumulation of matches," said Mourinho. "I could feel that in the second half (against Watford), he was going down and down and down.
"He's still a young guy and his body... his biological situation has space to improve.
"But in the first half, during the time, he had strength and explosion in his legs and he was dangerous and [scored] an important goal."