The Portuguese midfielder came off the bench with 22 minutes of normal time to go, helping the Red Devils charge towards a 5-0 win.
He grabbed the assist for Rashford’s first goal after 74 minutes, slicing the ball through the German side’s defence for the No.10 to slot into the net.
While he did not play a direct part in the goal that secured the hat-trick, the midfielder showed his influence in the move.
Passing the ball to Anthony Martial on the left wing, Fernandes continues his run towards the centre of the penalty box.
When the Frenchman starts running the same way, the United star cuts back towards the wing and drags three Leipzig defenders with him.
This gives the forward the room to find Rashford in the middle of the box, half-volleying into the bottom-right corner.
While the Bundesliga leaders were baffled, United fans recognised Fernandes’ run from the 4-1 win over Newcastle earlier this month.
With Ole Gunnar Solskjaer’s side looking to find the lead at 1-1, a counter-attack sees United’s hat-trick hero pick up the ball on the left wing.
The midfielder is hugging the touchline before cutting inside towards the penalty box as the Englishman continues down the left.
When Rashford steps inside, the 26-year-old adjusts his run to move towards the wing again.
And the Englishman picks him out with a back pass, leaving Fernandes free to slot into the top-right corner.
These clips were shared on Reddit, where the United faithful heaped praise on the Portuguese star’s tactics.
“Such an intelligent player,” one supporter said.
Another commented: “I just see rival fans’ tears.”
While a third simply added: “Bruno is class.”
While the forward is “destined to be captain” after making a selfless gesture to Martial in the win over Leipzig.