Barca were without Andreas Christensen, Eric García and Xavi Espart, leaving them fragile in defence, with 20-year-old midfielder Brian Farinas making his Champions League debut and just second start at right-back.
The hosts had not kept a Champions League clean sheet in 18 games, a run stretching back to April 2025, and there was real fear from seasoned Barca watchers that Villa would exploit their weakness.
In the first half Matty Cash, Gomes and Johan Manzambi, twice, made Barca sweat as the visitors created chances without taking them.
German Leon Goretzka hit the post in the second half but by then the game was done after Raphinha’s strikes.
Lamine Yamal, Anthony Gordon and Joao Cancelo went close to adding to Barca’s tally, but Emery remained philosophical.
“The test was definitely not in the level we want to achieve but there are a lot of things to learn, a lot of experience for the players and us,” he said. “It is giving me a lot of information to analyse and compete at this level.
“Overall, we are competing fantastically in the Champions League, although playing the match we played we have work to do to get to this level [of Barcelona].
“We were sometimes achieving it and close to scoring goals but we must be ruthless in the attacking third, 3-0 is maybe more than we deserved, but we accept the defeat.”
It was still a reminder of how far Villa have come under Emery, who took over when they were three points above the Premier League relegation zone.
A Champions League night against Barcelona in the Nou Camp was fanciful when the Spaniard walked in the door from Villarreal.
Since then, he has delivered the Europa League title and two Champions League campaigns and this defeat in Spain will be another key marker in Villa’s journey with him as they now prepare to visit Manchester United next on Sunday.
“Barcelona made the right decisions at the right times and scored really good goals,” captain John McGinn told TNT Sports.
“The manager spoke about being clinical at important moments in the game. When you come here, 50-50s sometimes don’t go your way. They also leave players up the pitch so if you lose the ball they can be away.
“I think we are competitive against teams at this level, we have shown that whether it is Bayern Munich or PSG. It was a huge learning curve for us and I am sure it will stand us in good stead for the future.”