Barcelona coach Hansi Flick warned their Champions League rivals his team are still looking to improve after beating Borussia Dortmund 4-0 on Wednesday.

The Catalans put one foot into the semi-finals with the first leg thrashing of last year’s runners-up at the Olympic Stadium.

Barca are the competition’s top scorers with 36 goals and their dynamic attacking trio of Robert Lewandowski, Raphinha and Lamine Yamal strike fear into the hearts of opponents.

“I want to keep improving, today we saw some points we can improve on,” Flick told reporters.

“We will analyse this game and I will tell the players they did very well, but there are still things to improve.

“I’m very happy with the result today but it’s just the first step.”

Raphinha netted his 12th Champions League goal of the season — he is the top scorer in the competition — and added two assists.

The Brazilian has 19 direct goal contributions this season in Europe, equalling former Barca great Lionel Messi’s record for the club.

“I always thought he’s an extraordinary player… the team is set on his shoulders, his dynamism,” said the coach.

His opposite number Niko Kovac was disappointed with Dortmund’s performance.

“It was a deserved defeat (but) we could have got a goal, as we all know the return leg will be very difficult,” said coach Kovac.

“I am optimistic but I have to be a realist… it was a very big result, our chances of going through are minimal.

“We know it will be difficult but we have to have a spark of hope, because without that spark it will be impossible.”

Meanwhile, Aston Villa coach Unai Emery insisted he still believes his side can get the better of Paris Saint-Germain and reach the Champions League semi-finals despite a 3-1 defeat in the first leg of their last-eight tie on Wednesday.

Villa took the lead in the first half in Paris through Morgan Rogers only for the hosts to turn the game on its head thanks to stunning strikes by Desire Doue and Khvicha Kvaratskhelia either side of the interval.

And a Nuno Mendes effort in stoppage time which gives PSG a two-goal cushion to take to Villa Park for the return appears to leave Emery’s side with a huge task to turn the tie around. “At 2-1 we were thinking about playing to win in the next match, and at 3-1 it is still the same,” Emery said.

“But we are here and enjoying it, and I am very proud of the players. We competed fantastically and we were close to getting a good result.

“At the end, with this goal, it is still more or less the same.

“Villa Park is our home, and hopefully there we will be stronger. But of course they are still favourites. They showed their power and individual quality.”

Villa came to the French capital on a streak of seven straight wins in all competitions which has boosted their chances of qualifying for the Champions League again next season and taken them to the FA Cup semi-finals.

However, it will likely now require a special performance in Birmingham next Tuesday for them to carry on their current run in the Champions League.

“I am not happy but I am satisfied with the performance of the team. It is special for us to be in Paris and playing a Champions League quarter-final,” Emery added.

“The second leg will be just as difficult at 3-1 as it was at 2-1. We have to win.”