The second leg takes place on Tuesday and only a major surprise will prevent Villarreal from bowing out at the semi-final stage, just like in 2006.
Liverpool is looking to win Europe’s biggest prize for the second time in four years, having also reached the final in 2018 under manager Jurgen Klopp.
Manchester City take a 4-3 lead over Real Madrid into the second leg of their semi-final in Spain next Wednesday.
A sea of yellow-clad Villarreal fans — at 5000 in number, they amounted to almost 10 per cent of the population of the town in eastern Spain — swarmed their way from Liverpool city centre to Anfield ahead of the game. And a rendition of The Beatles’ Yellow Submarine, which is the nickname of the visitors, was well-received by the lively away contingent before kick-off.
That was as warm as the welcome got.
Liverpool snapped into tackles and pressed high from the first whistle, meaning Villarreal’s players hardly got out of their half all match.
Yet, with Unai Emery setting up his team with his back four screened by a deep-lying and narrow midfield four, Liverpool were initially starved of space in what quickly became tantamount to an attack v defence exercise.
There were plenty of half-chances — Mane headed wide off his face, Mohamed Salah curled over then volleyed over, and Thiago Alcantara smashed a long-range shot off the outside of the post — but Villarreal held out until half-time.
Then it all went wrong.
The two goals came in between two disallowed efforts, by Fabinho then Andrew Robertson, and it was only Liverpool’s players taking their foot off the gas that stopped an even bigger victory.
Klopp used the opportunity to take a number of key players off early, with a potentially tough Premier League game against Newcastle on Saturday sandwiched between the six-day turnaround for the Villarreal games.
Liverpool are a point behind City in the title race, having reached the FA Cup final and already won the League Cup.
The quadruple charge is heading deep into May.