Jurgen Klopp felt Liverpool's ever-increasing Champions League experience was vital in their 6-1 aggregate quarter-final win over Porto, and dubbed his side "special" after they secured a semi-final place for the second consecutive season.

The Reds are the only side among 2017-18's semi-finalists to return to the last four this season and they progressed in some style as Porto were brushed aside 4-1 in the second leg at Estadio do Dragao.

Sadio Mane's second goal in as many games opened the scoring and there were further strikes from Mohamed Salah, Roberto Firmino and Virgil van Dijk as Liverpool absorbed plenty of Porto pressure while being ruthless in attack.

The introduction of Jordan Henderson and Firmino in the second half seemed to knock the last bit of steam out of Porto, and Klopp told BT Sport it was part of his game plan to have their fresh legs in reserve.

"In the second half it was clear that the energy level would drop a little bit for Porto so we could control the game much more and score the goals," said Klopp.

"It was clear the tempo would be lower because they couldn't cope with the tempo they had in the first 30 minutes. That was why we wanted to do it like this, so we could bring on Bobby [Firmino] and Hendo [Henderson] as well.

"We are more and more experienced, that's clear. We have had difficult away games at [Manchester] City last year, in Rome last year, and we knew this would be the same. They are a different animal in home games and it was clear we had to be ready for that.

"I think we are the only ones who were in the semi-finals last year and in the semi-finals again. That's really special for us."

Looking ahead to the clash with Barcelona, Klopp added: "It's the first time for me to play them, apart from a friendly and of course we are looking forward to that."

Jordan Henderson was warming up on the touchline when Mane put Liverpool in front on the night, and he said the decision to award the goal despite an initial offside flag was correct in his view.

"I thought [Mane's goal] was a goal to be honest, thankfully it was given and that gave us a real boost coming in at half-time," said Henderson.

"It was tough but that's what we expected. We had to be ready from the start, we dug in really well, they had some half chances and it was difficult in the first half."

Liverpool are away at Cardiff City next as their Premier League title push continues, and Henderson said there is plenty of belief in the squad.

"We believe but we've got to keep working hard," he said. "We try to give everything and be horrible to play against."