Barcelona thrashed visiting Borussia Dortmund 4-0 in their Champions League quarterfinal first leg on Wednesday, but Barca manager Hansi Flick was quick to silence suggestions that his side had already booked its place in the semifinals.

Flick played down Barca's sizeable lead ahead of next week's return visit to Germany.

"No, no, no, no, no, no, no, no... We are definitely not qualified yet! You never know what's going to happen, because football is just a crazy sport," Flick told Movistar Plus.

"To advance, we have to play in Dortmund like we did today, without making mistakes.

"We played very well, and when you play like that, you score goals, which is what happened.

"Winning by this many goals is important, and, when a team plays as well as that, goals normally do flow.

"We aren't thinking we are through, because you simply never know what might happen. Football is madness.

"We'll be determined to play like this again next week."

The return match is on Tuesday at Dortmund, which was last year's runner-up to Barcelona's league rival Real Madrid.

"We played very well, but we can't be thinking about the semifinals yet," Robert Lewandowski said. "We scored four goals at home, but we still have the return leg to play."

Undefeated since late December, treble-chasing Barca was once again boosted by brilliant performances of its attacking trio.

Lewandowski netted twice against his former club after Raphinha opened the scoring, while Lamine Yamal wrapped up the win.

But Flick also heaped praise on his defenders, who helped to keep a clean sheet.

" (Lewandowski, Yamal and Raphinha) are brilliant, and very important for us, but so is our defense and those who come on from the bench," Flick told a news conference.

"They have been showing that they can quickly make an impact and reach the same level as those who were on the pitch from the start.

"At this point of the season, with this schedule, it's so important that we keep all the legs fresh. So the team's depth is key.

"We played at a very high level, but we did make some mistakes and we can improve. Dortmund has very fast players, but we defended really well. I am very happy."

Spectacular stats

Raphinha added to his Champions League-leading tally by poking the ball into an open net in the 25th minute for his 12th goal in the competition this season. He then helped set up Lewandowski's first goal of the night in the 48th.

"I play with teammates of such a high level here," Raphinha said. "We all know each other really well, and that relationship level helps us as a team. Our stats are spectacular this season, and I just hope that it continues."

Lewandowski scored his 11th Champions League goal with a one-touch effort in the 66th, before Yamal closed the scoring in the 77th after another assist from Raphinha.

The 17-year-old Yamal has four Champions League goals, the highest by any player before the age of 18.

The 36-year-old Lewandowski has scored 14 Champions League goals since turning 35, two more than Cristiano Ronaldo.

Lewandowski scored 17 of his 105 career goals in the Champions League for Dortmund over three seasons from 2011-14.

The Poland striker is the Spanish league's leading scorer this season with 25 goals. He has scored 40 goals in all competitions.

Three's company

Lewandowski is the third player to score 105 Champions League goals, not counting qualifying matches, after Lionel Messi and Ronaldo, according to UEFA.

"In my head, I always want to be helping the team," Lewandowski said. "A striker always needs to be thinking about scoring goals, and, when the team plays well, it becomes easier for me."

Raphinha has scored in each of Barcelona's last four Champions League knockout stage matches, with seven goals in that span.

He entered the match with 11 goals, one more than Dortmund's Serhou Guirassy and Bayern Munich's Harry Kane.

Raphinha said he apologized to teammate Pau Cubarsi after the match for "stealing" his goal.

The defender's attempt was about to go across the goal line when Raphinha touched it.

Barcelona, a five-time European champion, last won the title in 2015.

Agencies Via Xinhua