His first Premier League goal was a 97th-minute winner for his childhood club to seal a 4-3 victory. No wonder Kobbie Mainoo was grinning ear to ear.
"I have still not come down from it. I still feel like I am dreaming to be honest.
"To start playing in the Premier League for my boyhood club has been amazing. Now it's about trying to win more games."
This was Mainoo's 11th senior appearance for United, with his previous games seeing him being quietly impressive in central midfield.
But this was something else entirely. This was a young man dragging his stricken comrades from the floor with a spark of individual brilliance to grab a win which United seemed to have thrown away.