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If the second leg of the Champions League quarterfinal plays out at all like the first it will surely be an impossible task for Liverpool to overturn a 3-1 deficit and advance past Real Madrid. If anything, the defending Premier League champions were lucky to return from Spain with just a two goal deficit after the gaps in their rearguard were remorselessly exploited by a direct, aggressive attack.

But there is still cause to hope for Liverpool, who under Jurgen Klopp have developed an impressive track record for comeback wins and late goals. They overcame a 3-0 deficit against a Spanish giant two years ago to reach the Champions League final, surely it is within their ability to repeat the trick again? If they are to do so, this is what needs to happen:

1. Revive the press

Though it was the defenders that failed to cut out Toni Kroos' passes that drew much of the post match focus last week, further discussion was perhaps merited on why it was that one of world football's best passers was given so much time to pick his spots. More could have been done to stop Vinicius Junior, Marco Asensio and Karim Benzema but it would have helped if they didn't have pinpoint passes floated in their direction from a man who had all the time in the world.

That Kroos and Luka Modric were so at ease in the engine room came down to two notable selection decisions Klopp made and probably should now reconsider: replacing Roberto Firmino and Thiago with Diogo Jota and Naby Keita. 

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The logic was apparent: Jota could bring the goals Firmino did not while Keita could make up for any shortfall in pressing that came without the Brazilian. Per 90 minutes, Keita is Liverpool's leading Premier League midfielder in successful pressures according to and he ranks in the 91st percentile among players in his position across Europe's top five leagues in that facet of the game. In 41 minutes he attempted to pressure Real Madrid players 14 times and was successful on just three occasions.

Without Firmino harassing Madrid at a deeper level, it was all too easy for Kroos to simply drop back, picking the ball up from his center backs and playing a pass in behind a high line with chasms of spaces to deliver it into. All three of Jota, Keita and Sadio Mane could have gotten closer to the German. None did. It is fair to assume that Firmino might have. It was equally notable that Thiago, perhaps not as natural a presser as others in the Liverpool midfield, was rather more successful at closing down the opposition midfield as Klopp acknowledged his tactic had not paid off.

What is curious is that the blitz pressing that Liverpool were the masters of early in Klopp's tenure has generally proven to be the most effective means of disrupting the Spanish giants in Europe. A revival of that sort of performance from the outset might at least ruffle Madrid's feathers early on. 

2. No errors at the back

"With the quality Madrid has you have to defend our your absolute highest levels, which we did not do the other night," Klopp said in his pre-match press conference. That is a generous assessment of his side's performance, one where they handed goals to Real Madrid. No error was more egregious than for the second, where Trent Alexander-Arnold flicked Toni Kroos' pass in behind into the path of Marco Asensio. It was one of several errors from the Liverpool right-back on a woeful night but he was far from alone.

Andrew Robertson offered nothing going forward to force Asensio back and Nathaniel Phillips and Ozan Kabak looked like what they are: two young central defenders utterly untested at the highest levels of European football. The importance of that cannot be understated. Alexander-Arnold and Robertson were hardly free from fault before but when you have defenders as quick as Joe Gomez or with the imperious streak of Virgil van Dijk there is little room for error.

There is little Klopp can do here but hope and try to restrict the supply line to VInicius and company, a point he emphasised in his post-match press conference. "He's obviously an outstanding talent. Everybody knew it before but since then he obviously became better.

"We try to avoid the passes in his direction, which is a big task actually. Impressed [with him]? Yes. Surprised? No."

3. Mane rediscovers some form

In the aftermath of the first leg most of the debate around Mane centered on a foul not given in the build-up to Real Madrid's second goal rather than his increasingly wayward shooting in front of goal. That has been a trend throughout this season, where has found the net on just 10 occasions in the Premier League and Champions League, an all the more curious slump considering he is taking more shots per 90 minutes in the top flight this season than he has since moving to Anfield, cracking the three shots per game mark for the first time in a Liverpool shirt.

Despite taking half a shot more than last season he is logging the same quality of shots per game -- as measured by expected goals (xG) -- and Opta's xG on target metric shows that a player who was averaging half a goal per game last season based on where his shots actually ended up is now only a small fraction over one goal per three games. In other words, Mane is getting into similar positions to last season but making far less of the opportunities that come his way. Just look at his shot points below, there are a lot of good quality looks in red.

Sadio Mane's shots in the Premier League and Champions League this season. The size of the bubble represents the xG value of any effort TruMedia

It is a precipitous decline and one that prompted Klopp to drop Mane for Firmino ahead the weekend win over Aston Villa, where he acknowledged that the Senegal forward's scoring slump had prompted the decision. Still if Liverpool could have confidence that they were getting their No.10 at something even approaching the peak of his powers come Wednesday he would start without a second's hesitation.

At his best Mane could strike terror into a Real Madrid side without Dani Carvajal and with Alvaro Odriozola only recently returned from fitness issues of his own. The 29-year-old is remorseless in his pressing, takes the chances that comes his way and has the most exceptional chemistry with Firmino and Mohamed Salah. With their attacking trident at the peak of its power, a 3-1 deficit is nothing Liverpool cannot overcome.

4. The players believe in Anfield magic

Sit at the top of the hulking Main Stand and the chasm that is Anfield strikes you. This was once a space filled to a deafening extent by a group of people who believed, no matter the opponent nor the context, that Liverpool were going to win. Since football's return behind closed doors it has felt like a far lonelier place, one where you can get trapped in your thoughts.  

Liverpool's great superpower in recent years has been that symbiotic link between those on the pitch and those off it. On occasion what seemed like a performative love-in brought titters of mirth from rival supporters -- never more so than when the Kop celebrated a 2-2 draw with West Bromwich Albion as though they had gone eight points clear at the top of the Premier League -- but that same crowd seemed to be sucking the ball into the net in comebacks wins over Borussia Dortmund (five years to the day since this game) and Barcelona.

"The result is a problem and the quality of the opponent [is too]," said Klopp. "There's just one extra problem - no supporters in the stadium. We have to create our own atmosphere."

Not having 50,000 people who believe in you implicitly certainly does not aid Klopp in convincing his players that they can overturn the odds but that does not mean it is impossible for momentum to build. Having a crowd urging you on in certainly important but in the end it was the players who overcame the odds against Dortmund and Barcelona. If they are 1-0 or 2-1 up with not long left to go there is no reason why they should not be able to repeat the trick.