"We never tend to make these Champions League semis easy for ourselves," observed Liverpool full back Alexander-Arnold after another European night of nerve-shredding tension.

Jurgen Klopp's men were so uninspiring and insipid in the first half on Tuesday night that goals from Boulaye Dia and Francis Coquelin had given Villarreal a shock 2-0 lead, obliterating Liverpool's two-goal advantage from last week's first-leg.

Suddenly, the Reds were staring at an embarrassing exit at the interval. According to stats provider Opta, Liverpool's three touches in Villarreal's box before the half were their lowest in a first half all season in all competitions. 

Would six-time winners Liverpool be the latest Goliath to be slain by the small-budget Villarreal, who had defied the odds to eliminate Italian giants Juventus in the last 16 and German powerhouse Bayern Munich in the quarterfinals?

However, the Spanish side could not maintain their stamina and composure in the second half, while Klopp's decision to replace Diogo Jota with Luis Diaz completely turned the tide. 

The Colombian striker injected much-needed intensity into the Reds and goals from Fabinho, Diaz and Sadio Mane saw them oust a resilient Villarreal and reach a third Champions League final in five years.

"To be in a final is never easy and to make this a third in five years is incredible from this group of boys," said Liverpool defender Andy Robertson "As fans and players, we should never take days like this for granted."

Robertson also singled out Diaz for special praise, saying, "He's been special. The talent he has, the will he has to win. He fits us perfectly. He made a big difference."

Klopp, meanwhile, was delighted to see the mental toughness that his players showed in the second half. "It feels so special because it was so difficult for us. Before the game, I told the boys I wanted the headlines to be the mentality monsters were in town," he told a press conference.

"The start was really difficult. We looked like we were impressed by them. We had no real build-up and we didn't play in the right spaces. We played into their hands. Our minds were not right. We felt the pressure. It was a football problem in the first half. And we had to solve it with football.

"I wanted it from the first moment, but the second half was like that. How we came back in the second half was so special. It was a top performance."

It's worth noting that on each of the nine occasions that Liverpool have won the first leg at home 2-0 in the competition, they have gone on to win the tie. And they now have ten aggregate wins from their last 11 European Cup/Champions League semifinals.

Mane's goal was Liverpool's 139th of the campaign, which set a new Reds record for most goals scored in a single season, breaking their tally of 138 from 1985/86.

The comeback win also means that Liverpool have become the first English club to reach the final of the European Cup/Champions League, FA Cup and League Cup in the same season. Their hopes of winning an unprecedented quadruple are still alive.

"It is really difficult – that is why nobody has ever done it before," beamed Klopp, in reference to the quadruple. "We will make sure we are ready for these finals. We will give it a go. That's for sure."

Liverpool will play the May 28 final at the Stade de France in Paris against either Premier League leaders Manchester City or 13-time European champion Real Madrid.

A much sterner test surely awaits the Reds, but they have shown that the team have what it takes to win the biggest prize.