"We played two games, and it's justified that we're through. I don't want to talk too much about my team, because it wouldn't be fair to Dortmund," said Flick.

"They made our lives very hard, but what was important is we made it to the semifinals."

Top scorer

Guirassy is Dortmund's "life insurance", coach Niko Kovac said, after a game that has further fueled his rapid rise to fame, and has seen him top this season's Champions League top scorer list. "Serhou just needs the support of his teammates, like every striker does, and he got that today."

Dortmund had arguably lost the quarterfinal in the first leg, and, in addition, had captain Emre Can and midfielder Carney Chukwuemeka ruled out through injury.

For a while, though, Guirassy made the impossible seem possible.

Guirassy missed chances in the first leg, and spurned a couple more early in Tuesday's game, but made no mistake from the penalty spot in the 11th minute, after Barcelona goalkeeper Wojciech Szczesny collided with Pascal Gross.

Guirassy's header made it 2-0 in the 49th minute, before an own goal by Ramy Bensebaini made Dortmund's task even harder. Fermin Lopez's low cross fired in off Bensebaini's ankle — a double disappointment for Dortmund because the defender been crucial in the comeback attempt, assisting Guirassy's second goal just five minutes earlier.

Guirassy pounced on Ronald Araujo's defensive error to complete his hat-trick with a powerful closerange shot in the 76th, in the process becoming the Champions League's top goal scorer so far this season with 13.

It gave Dortmund fresh hope of completing what would have been one of the all-time great Champions League comebacks — one to rival Barcelona's against Paris Saint-Germain in 2017 — but Barcelona held on to progress.