They face a monumental task to turn things around in next week's second leg at Anfield, especially knowing that, without an away goal, if they concede again they will almost certainly be out.

But Klopp refuses to give up hope.

"Because it is football, yes, but before this game we had a bigger chance let me say it like this," he said.

"It is difficult because it is Barcelona and they can play for counter-attack which doesn't help us a lot.

"Because it is football we should still try but it didn't make our life easier."

Despite the defeat, the scoreline was not an accurate reflection of how Klopp's side – hamstrung by having first-choice forward Firmino only fit enough for the bench and then losing midfielder Naby Keita to injury midway through the first half – performed.

There was a 20-minute period after half-time when they threatened so much that Barca coach Ernesto Valverde took off another former Red Philippe Coutinho and sent on another defender, switching to a 4-4-2 formation.

But Liverpool just could not take their chances and paid as a result.

"People who haven't seen the game will see the result and say strange things about it," added Klopp.

"As a manager, what I judge on is how we played. I am completely happy and proud of the boys.

"I think it was the best Champions League game we played not only this year but last year as well. Against a side like this, playing this kind of football, I was completely happy.

"Whatever happens, these boys, I couldn't be more proud of them."

Klopp said he was not surprised by Messi's brilliance but Valverde said he continued to be amazed.

"In these moments he is unstoppable. We couldn't defend the free kick. What a strike!" said the Liverpool manager.

"I knew before that Lionel was a world-class player and now I saw it again I am not too surprised to be honest."

Valverde, however, was full of praise for his talismanic forward.

"Messi always surprises you. I don't know how he does it," he said.

"He also does it in times when we need it. We also gained some breathing room with his runs to their penalty area when we needed it."

ga('create', 'UA-72310761-1', 'auto', {'name': 'pacontentapi'});
ga('pacontentapi.set', 'referrer', location.origin);
ga('pacontentapi.set', 'dimension1', 'By Carl Markham, Press Association Sport, Barcelona');
ga('pacontentapi.set', 'dimension2', '518d35dd-4c8d-4955-bd96-95f099acfc44');
ga('pacontentapi.set', 'dimension3', 'paservice:sport,paservice:sport:club-news,paservice:sport:football,paservice:sport:uk,paservice:sport:world');
ga('pacontentapi.set', 'dimension6', 'story');
ga('pacontentapi.set', 'dimension7', 'composite');
ga('pacontentapi.set', 'dimension8', null);
ga('pacontentapi.set', 'dimension9', 'sport:football');
ga('pacontentapi.send', 'pageview', { 'location': location.href, 'page': (location.pathname + location.search + location.hash), 'title': 'Jurgen Klopp will not give up hope after Barcelona defeat'});