Paris Saint-Germain v Bayern Munich
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The 3-2 in the first leg is highly likely to be repeated, given that both teams displayed defensive vulnerabilities that have characterised their entire campaigns. In short, both are porous between the lines, sitting in a decompressed shape that allows the attackers to burst straight through them, hence the toing and froing in Munich; once again, PSG and Bayern will cause serious damage in every transition.
More specifically, PSG's problems come from a lack of work from the front two. In a 4-4-2 when off the ball, Mauricio Pochettino knows he cannot afford to press high with Neymar and Kylian Mbappe leading the line, but their hunched formation was still weak. After a strong first half in which the forwards dropped to man-mark Joshua Kimmich, both abandoned their duties in the second 45 - leading to Bayern dominance.
As for Bayern, they were simply all over the place. Mbappe and Neymar, dropping into the number 10 space in typical Pochettino style, found plenty of joy because of a huge gap between Bayern's defensive and midfield lines. Neither team has improved in the space of a week, pointing to a repeat of the first leg.
Chelsea v Porto
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Thomas Tuchel's reign as Chelsea manager has been defined by cautious and careful building of possession, with a fine-tuned structure and a midfield-heavy 3-4-2-1 ensuring that Chelsea are always in control of a contest. That is the best way to control the variables of pandemic football, as Pep Guardiola has shown at Manchester City, hence why Tuchel has done none of the tactical tinkering he was known for at PSG.
Rhythmic possession and territorial dominance was the theme of the first leg win at Porto, and it will be the theme again. Sergio Conceicao's side sit in a conservative 4-4-2, rarely pressing and inviting the opponent onto them. The idea is to channel the energy of that famous Jose Mourinho team and, while it worked in unsettling Juventus, Chelsea will not be drawn in.
In fact, Porto's need to come out of their shell more will favour the hosts, who through Mason Mount and a rejuvenated Kai Havertz should be able to pierce through once Porto open up. There is no hope for the Portuguese side, not after the Blues' scintillating high-tempo display against Crystal Palace.
Liverpool v Real Madrid
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The first leg in Madrid was defined by Liverpool's passivity in central midfield. Naby Keita had a particularly poor game but the whole team was off the pace, failing to apply any pressure to the Real Madrid players - who used their experience to work out a simple but effective tactical strategy. Toni Kroos got his head up to ping longer balls over the top of the Liverpool defence, setting Vinicius Junior away.
Jurgen Klopp certainly won't start Keita again, and with Liverpool chasing two goals he may even go for a 4-2-3-1 with four forwards on the pitch. Whatever the formation, we can guarantee Liverpool will have learnt from their mistakes and, at Anfield, will be much sharper in the press. That may unsettle Real somewhat, although ultimately there are too many flaws in the Liverpool defence for Klopp to turn this one around.
As Liverpool push forward in search of goals, that shaky pairing of Nat Philips and Ozan Kabak will hold an uncomfortably high line, offering even more room for Vinicius on the counter-attack. Real will happily soak up more pressure before hitting long passes in behind the Liverpool centre-backs.
Borussia Dortmund v Man City
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We are now in the territory where Pep Guardiola has one of his Champions League moments, unnecessarily complicating things with a tactical plan that doesn't come off. We cannot predict what that might be, of course, and so instead will focus on how Borussia Dortmund will look to turn this game around. First of all, they will come out with a confrontational approach, having been considerably worse when pushed onto the back foot in the final half hour.
But as Phil Foden and Kevin de Bruyne inevitably dominate the ball and put Dortmund into uncomfortable positions, there becomes a distinct possibility that Erling Haaland - quiet in the first leg - will come to life on home soil. The high line of John Stones and Ruben Dias is certainly vulnerable to Haaland's pace and power, as seen when the young striker went one on one with Ederson at the start of the second-half.
However, that does not mean Dortmund are favourites. They continue to have problems in the full-back areas, where the wingers are rarely seen helping out, and that should give Riyad Mahrez and Foden the space they need to create chances. Both players danced through the lines far too easily in the first leg; both will expect to be more ruthless this time around.