Manchester United boss Jose Mourinho described Marcus Rashford as "a kid who is in love with football" after his superb free-kick saw off Celta Vigo.
The 19-year-old fooled Celta goalkeeper Sergio Alvarez with a second-half set-piece to ensure United take an away goal and 1-0 lead back to Old Trafford for next Thursday's second leg of the Europa League semi-final.
Rashford has scored four times in under a month including a dramatic extra-time winner against Anderlecht in the quarter-finals, his form coming at a vital time with Zlatan Ibrahimovic out injured.
And Mourinho hailed the England international's dedication after his strike proved decisive at Balaidos.
"Marcus Rashford is a 19-year-old kid who is in love with football," Mourinho said to BT Sport.
"He is a kid who stays after training for half an hour more to practice taking free-kicks and waits for the opportunity.
"It is his mentality. He works and works and works. He is very mature so let's forget the age because what matters is not the age, but the quality."
Mourinho added at his post-match media conference: "He worked really hard and caused them problems. He had a fantastic shot in the first half with that beautiful save and then the free-kick is work - he works every day and loves to work.
"Sometimes a training session finishes for the group and he keeps doing his individual work with my assistants. The free-kick is really well taken and I think the goalkeeper has no chance because the ball is really fast."
There was a scare for United late on when Rashford appeared to limp off and Anthony Martial replaced him, but Mourinho did not seem overly worried.
"He started the game with a little problem and with all the running and continuity he was feeling it," said Mourinho.
"Martial was fresh and he had to give us the last 10 or 15 minutes where we thought we could still score because of plenty of space to play."