They feared Luis Suarez would hurt them and he did. He said he would celebrate and he did.
They worried about Lionel Messi and they were right to. They fretted about Barcelona and with good reason.
They talk about fine margins at the highest level and no wonder.
Liverpool face a monumental task if they are to turn around this Champions League semi-final. How can a team contribute so much to such a wonderful, absorbing contest and find themselves on the end of a 3-0 shelling?
There is no hiding place in this competition, no hiding place in this stadium. As Camp Nou rocked and rolled and revelled in another Messi masterclass, for Jurgen Klopp and his side there was only the harshest of lessons.
Take your chances. Because if you don’t, then the best will.
With 15 minutes to go this game - and this tie - was very much in the balance, Liverpool on top after falling behind to Suarez’s fine first-half strike, but unable to turn a series of promising positions into something more useful.
Sadio Mane missed a golden chance, Marc-Andre ter Stegen denied Mo Salah. James Milner hit the goalkeeper when he had to find the corner. The goal was coming, coming, coming.
It came, alright. But at the other end.
With a stroke of good fortune, Barcelona got their second. Suarez’s shot hit the bar, Messi was first to the rebound and suddenly everything changed.
A slim deficit became a mountain. A promising performance became a 15-minute nightmare, with Messi delivering the killer blow, a knife to the heart delivered in the most beautiful manner imaginable.
His 30-yard free-kick was a work of art, speared into Alisson Becker’s top right-hand corner with otherworldly brilliance. It may have broken Liverpool’s resistance once and for all.
This is the reality of this level, a level that Klopp’s side showed they belonged at for 75 minutes. How, he will wonder, can they come away with nothing having given everything?
They still should have taken something, even though they lost their shape and their heads in the closing stages.
Had Salah converted a golden chance at 3-0, we would be talking about away goals and the chance of a salvage job at Anfield. Instead the Egyptian, who had performed magnificently for the most part, hit the post with the goal gaping. It summed up Liverpool’s night.
"You can lose away," said Klopp afterwards. "But only as long as you score. That was the problem tonight."
His side had fallen behind to a piece of predatory brilliance, Suarez’s razor-sharp movement and anticipation allowing him to meet Jordi Alba’s beautifully-judged low cross in the 26th minute. It was his first Champions League goal in more than a year; just like the last one, it came against Alisson Becker.
Suarez, as he had promised, celebrated wildly. He gave Liverpool fans the most wonderful of memories, but there was no sentiment here. The Uruguayan was his gnarly, aggressive self, ruffling feathers, treading on toes, pulling shirts, scoring goals.
Liverpool rallied. They defended strongly and smartly, with Joel Matip excelling. They worked and they worked, and they found space with regularity. Gini Wijnaldum, the surprise choice to start as the No.9 with concerns over Roberto Firmino's fitness, pressed and harried and opened up space, Salah terrorised Jordi Alba and Clement Lenglet, Mane might have had a penalty when bundled into by Gerard Pique.
They lost Naby Keita to an early injury, but Jordan Henderson slotted straight in. The captain’s sublime pass released Mane before the break, but he sent his shot over. What did we say about harsh lessons?
The reality is that Liverpool could now face agony at home and abroad in the next week. This most wonderful of seasons could end in heartbreak. Twice.
They must beat Newcastle in the Premier League on Saturday and hope Manchester City stumble against Leicester on Monday. Twenty four hours later, they must attempt to scale Mount Everest in the second leg at Anfield.
Not impossible. Barca lost a three-goal lead against Roma in last season's quarter-finals, and writing Liverpool off is rarely a smart move. This club, after all, has a history of glorious fightbacks.
If they turn this one around, though, it might just top them all.