Ralf Rangnick urged Anthony Elanga to "make the defenders scared" before he notched a late equaliser at Atletico Madrid.
The Manchester United star came off the bench with 15 minutes left and his strike cancelled out Joao Felix's opener in the Spanish capital.
United hadn't even mustered a shot on target before Elanga's effort as Atletico dominated for long periods.
The teenager has continued to receive opportunities under Rangnick and his strike repaid that faith.
Bruno Fernandes sent him through and he was able to fire across Jan Oblak in to the far corner.
Elanga said after the game: "He (Rangnick) said to me, do what I always do, make the defenders scared, run in behind, and when I get an opportunity, take it."
The goal means it will be winner takes all at Old Trafford in three weeks time after the stalemate in Madrid.
The Champions League remains United's only chance of silverware this term, although they are not fancied to make the business end of the competition.
Elanga is one of several academy products operating in the Red Devils first team and has longed to make an impression on the European stage.
"I've dreamt of moments like this, scoring in the Champions League," he added.
"It's only the first half, the first half is done now and the second half is at Old Trafford in a couple of weeks, so we have to be ready for that."
Elanga is up against some serious competition when it comes to getting minutes under his belt.
The likes of Cristiano Ronaldo and Marucs Rashford both started at the Wanda Metropolitano, with Elanga replacing the latter in the second-half.
The teenager conceded his side were far from their best, but was determined to make an impact.
He continued: "When I get an opportunity for the club I just want to repay the favour for the manager and leave nothing in the tank and give 150 per cent every time I step on to that pitch.
"I just do what I can do when I get on the pitch. I always tell myself I am going to be the best player on the pitch and leave as the best player on the pitch.
"Obviously, we did not play the best football in the first half, and then in the second half with the substitutions that we made, we stepped up a bit.
"I wanted a good result for the fans because they travelled a long way, and hopefully the next leg at Old Trafford will be even better."
