Nothing, perhaps, should give Liverpool such heart ahead of Saturday’s Champions League final as Bayern Munich’s first goal against Real Madrid in the second leg of their semi-final.

Nothing dramatic happens. Franck Ribéry turns in from the left flank and plays an unremarkable low pass in to Robert Lewandowski in a central position on the edge of the box. The ball bounces up in front of the Polish striker and his first touch as a result takes him away from goal. He is able, though, to shield the ball and, as Sergio Ramos decides to sit off, Lewandowski has time to work the ball wide to Thomas Müller who is, bafflingly, in 15 yards of space, out on the touchline, roughly level with the edge of the box.

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Marcelo, the Madrid left-back, has been drawn into the centre, tucking in as though anticipating that Lewandowski might allow Ribéry’s pass to run across his body and then turn Ramos. That much is reasonable. What is not is what then happens. Marcelo must have been aware of Müller’s presence. Müller is, after all, his primary concern. As soon as Lewandowski’s touch took him away from goal and Ramos didn’t lunge in (and nobody can blame Marcelo for thinking that he might), Marcelo should have been closing down the space. Instead, he dropped back, five yards behind the defensive line, and only then moved left to shut Müller down.

By then it was probably too late, although Marcelo dawdled, hanging back in a no man’s land when a sprint might still have pressured the cross. Ramos, slightly half-heartedly, did cut out the cross at the near post, but his indecision knocked the ball down for Joshua Kimmich, who scored.

Marcelo is perhaps the finest attacking left-back in the world. That deal that took him from Fluminense to Madrid in 2007 for around £5m may, pound for pound, be the greatest the club has completed. In the majority of the games they play, Marcelo is perfect for Madrid. He works up and down the line. He is quick. His touch is superb. He can cross. He scores a couple of goals a season. The only problem comes when he has to defend. Most of the time he doesn’t have to, but he surely will in Kiev.

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If Mohamed Salah is gifted the sort of space on Saturday that Müller was in that second leg, and if he produces anything like the sort of form he was showing a month ago, Liverpool will devastate Madrid on that flank. Normally, that would be enough to give them a clear edge, but this is anything but a normal game. None of the usual rules seem to apply.

Nothing Trent Alexander-Arnold did in Rome was quite as eye-catching as Marcelo’s dilatoriness for that first Bayern goal, but equally the way Stephan El Shaarawy exposed him in the second leg will have not have gone unnoticed by Madrid. In part, of course, that’s because Salah was exempted from defensive duties that night, seemingly instructed to remain high up the pitch and occupy the space behind Aleksandar Kolarov so that every time Liverpool regained possession there was an obvious and dangerous out-ball.

Facebook Twitter Pinterest Marcelo is perhaps the finest attacking left-back in the world – the problem comes when he has to defend. Photograph: Chris Brunskill Ltd/Getty Images

Whether Madrid play a 4-3-3 or, more likely, a 4-3-1-2 with Isco tucked behind Cristiano Ronaldo and Karim Benzema, Alexander-Arnold will surely be targeted. The question for Jürgen Klopp is then whether to have Salah drop back and help out defensively, or to call Madrid’s bluff and risk them doubling up on the full-back for the potential reward of Salah constantly in space high up the pitch behind Marcelo.

In most games it would be enough to say the battle on that flank would be decisive. But here it feels inadequate. Dani Carvajal did return, after a month’s absence, to play the full 90 minutes against Villarreal on the final day of the league season, which means he, rather than the converted winger Lucas Vázquez, will play at right-back. But if there is any doubt about his fitness it will be sorely tested by the pace of Sadio Mané, particularly if Andy Robertson can get up to support him – which he should be able to do if Madrid play a 4-3-1-2 and focus on trying to expose Alexander-Arnold on the other flank.

And then there’s the question of the centre. Ramos is a fine defender in one-on-one situations, but how will he and Raphaël Varane cope with Roberto Firmino dropping deep, leaving them with space to mark until Salah and Mané dart into it?

A repeated problem for Liverpool under Klopp has been the lack of protection afforded their back four when they lose compactness and space opens up in front of it. The nature of their pressing game means there is no natural holding player to sit in. That is a major concern and one that Isco, tucked behind two forwards, could be ideally placed to exploit.

Everywhere on the pitch, it seems, on both sides, there are defensive flaws that might be exploited. And that’s what makes this final so hard to read. It’s not just that either side could win, it’s that either side could win by a wide margin.