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Defeat at Anfield in the first leg ended Villarreal's five-match unbeaten run in all competitions. They had lost three of their previous five matches, winning the other two, before that unbeaten run.

The Yellow Submarine also come into this game off the back of a defeat after going down 2-1 at Alaves in La Liga. Samu Chukwueze scored their goal, his third in the league this season and his first since 18 December.

Liverpool have lost their last four away games at this stage of the Champions League, conceding 11 goals.

They lost 3-0 at Barcelona the last time they were here in 2019 (although that worked out pretty well in the end), lost 4-2 at Roma in 2018 and were beaten 3-2 after extra time at Chelsea in 2008 and 1-0 by the Blues the year before.

Liverpool have not lost an away match by a two-goal margin since... oh, interesting... the 3-1 defeat at Real Madrid in last season's quarter-final first leg.

Villarreal have won three of the seven European ties in which they have lost the first leg away, suffering elimination in the most recent, against Lyon in the 2017-18 UEFA Europa League round of 32 (1-3 a, 0-1 h).

The only time they have turned around a two-goal away defeat was in the 2002 Intertoto Cup third round, when they beat Torino on penalties after the teams had both won 2-0 at home. That is Villarreal's sole previous 0-2 first-leg away defeat, the Lyon tie the only other in which they had to retrieve a two-goal deficit at home in the second leg.

Remember that the away goals rule is not in play this season so if Villarreal win by two goals we'll be heading to extra-time and potentially penalties.

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Jurgen Klopp has said in-form Liverpool midfielder Thiago Alcantara could play in any team in the world, club or international.

Thiago has not played a full 90 minutes for Spain in two years but, as he travels to his homeland to play Villarreal in the semi-final of the Champions League, Klopp has stressed the brilliance of his playmaker.

“In the shape he is now, Thiago could play in each team in the world,” he said. “In fact, not only would he play in it, but he would be the outstanding footballer.

“All Thiago needs is to be fit and to gain some rhythm, and then he shows his best football. Physically, as long as he’s in the right shape, he shows everyone how good he is and he was injured when he arrived here."

Spain boss Luis Enrique is spoiled for choice in midfield, with Atletico Madrid duo Koke and Marcos Llorente taking up the central spots in their most recent fixture against Iceland in March.

“Of course, Spain have a lot of options and are an incredibly talented football team,” said Klopp. “At this moment, Thiago is showing his best football and is the outstanding footballer.”

Liverpool were delighted recently when Jurgen Klopp decided to extend his contract with the club until 2026.

However, Trent Alexander-Arnold says the news "has not really sunk in" because the players are so focused on their relentless pursuit of silverware.

Klopp signed a new two-year deal last week but Alexander-Arnold stressed that the team are concentrating on what they want to achieve.

"The gaffer is making something special for us here, and of course it gives us a boost," he said. "Hopefully the extra two years will be just as successful as the ones we've had with him so far.

"But it wasn't like a big celebration or a giant party - I think we were all at home when we found out!

"It's hard for the news to sink in when the games are coming thick and fast. Obviously, it's something we want to hear, but the manager does not want to distract us or take our focus away.

"It's very much business as usual."

Alexander-Arnold said earlier in the season that a club of Liverpool's size should be targeting a minimum of one trophy a season - but with four in their sights, he's revised that aim for the 2021-22 campaign.

"We're in fine form and finding all kinds of ways to win," he said. "This is the time of the season we find most exciting.

"If we win all our games in May, we'll have our hands on a few more trophies."

One thing you can guarantee tonight is that it will be lively in this ground, certainly while Villarreal are still in the tie. It's a tight, little ground that will be awash in a sea of yellow. The home fans give just a little taste of it with some noisy cheers as the home players emerge for the warm-up.

Villarreal did win 1-0 against Bayern Munich at the Estadio de la Ceramica to help them reach this semi-final stage.

However, in more encouraging news for Liverpool, the first-leg win against Bayern is one of only two Villarreal victories in their last ten games at home in the Champions League, group stage to final (D5 L3), the other coming against Young Boys on Matchday 4 this season.

They did, though, win all six home games in last season's Europa League and were unbeaten in eight home European matches (W7 D1) before losing to Manchester United on Matchday 5.

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The two teams' only previous meeting in Spain came in the semi-final of the 2015-16 Europa League, with Adrian Lopez scoring the only goal of the first leg in Spain to earn victory for a Villarreal side coached by Marcelino.

However, the Reds went on to win the second leg 3-0 to reach the final.

We've done it the other way round this time, but that 3-0 second-leg scoreline on home turf is exactly what Villarreal are aiming for tonight.

By another little quirk of fate, Klopp's side were beaten in the 2015-16 Europa League final by Sevilla, managed by none other than Unai Emery.

Oh, and in case you were wondering here is said radio pundit slating Villarreal after their first-leg display at Anfield...

Guillem Balague
Spanish football journalist

Guiding unfancied Villarreal to the Champions League semi-finals ought to have been a career highlight for Unai Emery, the manager who has taken a team from a town with a smaller population than Clacton-on-Sea to the pinnacle of European football.

Yet a common theme of the Yellow Submarine's run to the last four of the continent's premier competition has been the criticism directed at the 50-year-old former Arsenal boss.

After knocking out Juventus in the last 16, the Italian side's manager Max Allegri was unhappy with what he perceived to be Villarreal's defensive approach, ignoring the fact the Spaniards had the majority of possession in the first leg and, with the tie delicately poised at 0-0 at half-time in the second leg, that it was Emery's team who went in search of victory. They scored three times in 45 minutes to progress.

In the quarter-finals, Villarreal stunned Bayern Munich, whose manager Julian Nagelsmann also criticised Emery's tactics. Nagelsmann conveniently forgot that in the first leg, the La Liga side had missed a number of chances that could have earned them a more convincing lead.

Then came the semi-final against Liverpool and the fiercest condemnation yet following a 2-0 defeat at Anfield, a scoreline they will attempt to overturn in Tuesday's second leg.

One UK radio pundit described Villarreal as "a disgrace" to the Champions League, calling them "pathetic".

That view was quite rightly rejected by just about everyone from both sides, with the reality being that Villarreal have a budget of just under £100m, while Liverpool's is around six times that amount.

All that criticism begs the question: Does Emery get the respect he deserves?

Read more from Guillem Balague, as he strives to answer that question here.

John Guy: Got strange feeling that Villarreal will do the impossible and knock out Liverpool tonight.

Dion Dublin
Former Premier League striker on BBC Radio 5 Live

Villarreal have got a chance without a doubt. Everyone is trying to resist Liverpool at the moment as they’re so potent.

Diogo Jota coming in, it’s the trust element. He’s not a gamble [compared to Luis Diaz]. You need a player like that.

He’s gone with legs and energy in midfield, with Jordan Henderson on the bench.

Chris Sutton
Former Premier League striker on BBC Radio 5 Live

I think Jurgen Klopp has great options in all areas. He can rotate. At the weekend he could leave Salah on the bench, we couldn't have thought that possible two years ago.

That's the confidence and strength in depth they have. Luis Diaz has hit the ground running. Diogo Jota has been a sensational signing. With them going for four trophies Klopp is able to rotate the squad to good effect.

It's been hammering it down with rain all day in Villarreal but that't not dampened the mood. The atmosphere is building...

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

• Liverpool won all five Champions League away matches this season, by an aggregate score of 15-5. The Reds can become the first club to win more than five Champions League/European Cup (excluding qualifying) away games in a single campaign.
• Jurgen Klopp has progressed from all of his four European semi-finals as a manager (one for Borussia Dortmund, three for Liverpool). In all four of those ties, his team won the home leg and lost the away leg.
• The Reds conceded at least three goals in the away leg of their past three Champions League semi-final ties: 3-2 defeat after extra-time versus Chelsea in 2007-08 (second leg), 4-2 loss to Roma in 2017-18 (second leg) and 3-0 defeat at Barcelona in 2018-19 (first leg).
• They've won four of their five penalty shootouts in European competition, including all three in the Champions League/European Cup. The only defeat was by Besiktas in the 2014-15 Europa League last 32.

Chris Sutton says Liverpool will face a tougher test against Villarreal in Tuesday's Champions League semi-final second leg and added it would be one of the biggest shocks in Champions League history if Unai Emery's side turned things around.

The former Premier League striker told BBC Radio 5 Live: "Villarreal have to come out and be more expansive than they were at Liverpool if they want to get back in it.

"The first goal is going to be absolutely crucial, but I think Liverpool are going to be in for a sterner test - they have to be. Villarreal went to Anfield too contained. Once the first goal went in and Liverpool got the second you’re thinking it’s a long way back for Villarreal.

"But throughout this competition they have knocked out Bayern Munich and Juventus, and I’m sure Jurgen Klopp won’t be underestimating them. Liverpool were so dominant [in the first leg], but Jurgen Klopp won’t let them switch off. They are too professional for that. What Liverpool can’t do is let Villarreal back into this tie and give them any encouragement.

"We're all expecting Liverpool to go through and will be one of the biggest shocks ever in the Champions League if Villarreal can turn it around."

Hear more on tonight's game and Liverpool's quadruple chances on BBC Sounds

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Villarreal have a fair old army of ex-Premier League players to choose from in their squad. It's hard to make a case for any of them being a roaring success in the English top-flight...

Juan Foyth (Tottenham 2017-20)Étienne Capoue (Tottenham 2013-15, Watford 2015-21)Francis Coquelin (Arsenal 2008-18)Vicente Iborra (Leicester 2017-19)Dani Parejo (Queens Park Rangers 2008-09 loan)Arnaut Danjuma (Bournemouth 2019-21)Serge Aurier (Tottenham 2017-21)Giovani Lo Celso (Tottenham 2019–-2)

As a group, they're doing pretty well in Spain (and in Europe), though.

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As you'll definitely be aware by now, Liverpool are going for a quadruple of trophies this season.

They already have the Carabao Cup in their possession, are second in the Premier League, into the FA Cup final and are looking to seal a Champions League final place tonight. Greedy.

As BBC Sport's Chris Bevan explains in the piece he wrote on the site about this very topic, since it first became achievable in 1960, there have been 120 other attempts by 15 clubs to become champions of England, conquer Europe and win the FA Cup and League Cup in the same campaign.

We have seen three different trebles from those teams and 17 more did a double of some kind. But, date-wise, no side has got this far into the season with their hopes still alive of an amazing clean sweep.

So if it's potential quadruples that float your boat, click on here to head on over to Chris' piece for an in-depth read.

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Villarreal, managed by former Arsenal boss Unai Emery, qualified for the Champions League after beating Manchester United in last season's Europa League final and have eliminated both Juventus and Bayern Munich on their way to the last four.

However, the Spanish side are only seventh in La Liga, nine points adrift of fourth-placed Atletico Madrid in the final Champions League spot, with four league matches remaining.

Therefore, if Villarreal fail to win the Champions League this season, it is very unlikely they will be playing in the competition in 2022-23.

"We need to play a perfect game," admitted Emery on Monday. "It is a difficult task, but we're working on the game.

"We need to find our excellence in certain things and maybe achieve something no-one has achieved, which is this kind of comeback.

"We will try to find some weak spots, something that no-one has done this season."

Former Villarreal midfielder Marcos Senna says the club's Champions League run may have impacted their league form this season, but believes the La Liga outfit have nothing to lose heading into tonight's second leg against Liverpool.

“Obviously we are really focused on today," said Senna. "It is a historical game and very complicated but every game is a different story.

"We are at home, have nothing to lose and let’s see what happens - we know the team is going to try their best throughout the 90 minutes.

"Because we had to play in the Champions League this season, we have not been very consistent in our league games, we lost points against teams that were below us in the classification, that is why we are ranked seventh now.

“But we have a good squad and we can really fight for a spot in the Europa League. If we hadn't played the Champions League this season, maybe we would be fighting to qualify among the top four and qualify for the Champions League next season, but I feel very proud of the work we have done this year."