They took his tournament-leading tally to 10 this season.
Within 20 minutes, however, the Red Devils were left red-faced and on their way out of the competition, as the brilliance of Lionel Messi and an inexplicable blunder by one of the world's best goalkeepers left the English side with an impossible task. "We've said all along that this won't change overnight and the next few years will be massive to get to the level teams like Barcelona are at". Because we've got good players and I've got good players to work with. "I was fortunate the first went in, I struck it hard and just inside the post".
The goals ended Messi's weird scoring drought in Champions League quarter-finals that had reached 12 matches dating back to 2013. However, two of those instances have been in this season's competition, including once by Manchester United.
Jesse Lingard's 79th-minute shot from distance was a rare second-half highlight for United, while the introduction of former Barca star Alexis Sanchez for Lingard a minute later brought a round of applause from the home fans as they recognized the arrival of a former player.
In La Liga, he's the top scorer with 33 goals.
Moments later, Barca doubled their advantage and it was down to yet more errors.
Messi opened the scoring with a brilliant solo effort in the 16th minute after he won possession of the ball, ghosted past a defender, and curled a shot into the far corner.
United started the game in excellent fashion as Marcus Rashford clipped the top of the bar after little more than 30 seconds.
Both could have been avoided, even if Young's turn on the edge of his own box was punished in devastating fashion.
The second was simpler. Fred again was caught in possession and the ball fell to Messi, who could only produce a weak effort - but it was enough to squirm under the body of an embarrassed De Gea.
Messi could have had his hat-trick too after Luis Suarez found him with a superb cutback and there was an nearly comical sequence in the second half when the Argentinian played with his United chasers before finally being bundled over by McTominay.