The Reds are set to welcome the Liga giants to Anfield on Tuesday for the second leg of a European semi-final that they currently trail 3-0.
Jurgen Klopp’s side have it all to do in order to book their place in a Madrid showpiece on June 1, but club legend Dalglish believes anything is possible despite recognising the size of the challenge.
He told the Sunday Post: “Of course, it’s hard to see any team scoring four against Barca to get through. But I do think the tie is still open, and there remains a glimmer of hope. It would be foolish to say the tie is over.
“Jurgen Klopp said he felt it was the team’s best away performance in two years, and it’s hard to argue with that.
“Firstly, I believe Liverpool showed in the first leg that they are fitter and stronger than their opponents. Also, with the game being at Anfield, the backing from the home support will drive the players on.
“There is also a rich history of comebacks by Liverpool in Europe over the years, and that’s why I’d never rule out that being the case again.
“That said, if the players were to overturn this three-goal deficit against Barcelona, it would be the greatest comeback of them all, no question.”
If Liverpool are to complete a stunning turnaround on home soil then they will have to find a way of keeping Barca talisman Messi quiet, with the Argentine having netted twice against them at Camp Nou.
“In Lionel Messi, Barca also have one of the finest footballers the world has ever seen,” added Dalglish.
“He will turn 32 next month but shows no signs of letting up. Messi continues to break record after record, and his hunger to succeed looks every bit as strong as it was 10 or 12 years ago.
“The way he just glides past players as if they aren’t there is unbelievable. I don’t envy any defender having to try to stifle him. In footballing terms, it’s as close to being as an impossible task as you could get.
“People always want to get into the debate about whether he is the greatest at the moment, or is it Cristiano Ronaldo?
“It used to be whether Maradona or Pele was the greatest of all time. As I’ve said many times, it’s all down to opinion. It can’t be factual.
“My answer is that we are extremely fortunate to have two such outstanding players in the game at the same time and you just enjoy them – not try to compare them.”