Liverpool head to Porto in the Champions League quarter-final having secured an important 2-0 first leg victory at Anfield last Tuesday.
It was on the whole a fairly routine victory for the Reds against their Portuguese opponents, with goals from Naby Keita and Robeto Firmino securing the result.
However, Porto were not without chances and did, on occasions, look to threaten Liverpool’s backline.
Jurgen Klopp himself admitted Liverpool were taken by surprise by Sergio Conceicao’s approach to the game, abandoning his usual 4-4-2 formation for a 5-4-1 set up.
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“We didn’t know before the game Porto would do it like this,” said the Reds boss. “How could we know that Maxi (Pereira) and (Jesus) Corona would play together?”.
He continued by saying “Of course, their formation surprised us but we saw it immediately. The players saw it”.
Klopp’s surprise was understandable. Conceicao only sparsely adjusts his 4-4-2 formation and almost never deploys a 5-4-1.
In the formation, Porto remained compact to limit the spaces between their lines and to prevent Liverpool from playing through them - most likely looking to avoid a repeat of the first-leg 5-0 hammering they suffered last season.
They also elected not to press Liverpool aggressively when the Reds were in possession.
Their Passes Per Defensive Action (PPDA), which focuses on how many passes a team allows before pressing to regain the ball, averaged out at 20.96 at Anfield.
This is significantly higher compared to their average across all competitions this season of 6.15.
As a result, the Reds' centre-backs were granted plenty of time to progress to the halfway line and play out to the wide areas.
Due to the omission of Andy Robertson through suspension, James Milner was deployed at left-back.
Whilst defensively he was assured, it did have an impact on Liverpool’s attacking prowess down that side - something Porto seemed all too aware of when deciding to deploy their narrow compact shape.
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In the two games either side of the Porto match against Southampton and Chelsea, Liverpool averaged 56.5% of their crosses from the left side with Robertson.
However, against Porto, that percentage dropped to 28%, with the Reds favoring the right side and Trent Alexander-Arnold.
For the return leg at the Estádio do Dragao, the Scottish defender will surely be restored and will be a key component to Liverpool’s attack.
Whilst Porto’s set up did present Klopp’s with men the lion's share of possession, they were caught out several times on the counter-attack.
Due to the ease in which the Liverpool’s backline could progress high up the pitch with the ball, when Porto regained possession in their own half, they found success in playing long balls over the top and into the space exposed behind Liverpool’s defence.
In the below sequence, a Liverpool attack breaks down and Porto are able to counter.
Note how high up the pitch Liverpool’s defenders are - out of picture Virgil Van Dijk is the deepest Liverpool player on the pitch.
A simple lofted ball over the top bypasses three of the four Liverpool defenders and heads towards the onrushing Porto attacker Francisco Soares.
From here, Liverpool’s defence are left to scramble back into position.
Their best-case scenario is that Soares' first touch slows him down enough to allow Van Dijk to stand him up into a 1v1.
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However a good touch by the attacker could be enough to put him through onto Liverpool’s goal in a 1v1 with keeper Alisson Becker.
Thankfully, Van Dijk does enough to force him out wide and close out any immediate danger resulting in the attack petering out into nothing.
As the game progressed, Porto became more reliant on longer balls in this counter-attacking style. In this match, their average pass length increased from their season average of 20.46 to 22.28.
The success Porto found deploying this tactic was something that Klopp didn’t enjoy.
Post-game he said: “We lost a bit of direction and didn’t play that clear any more. We were still around the box and all that stuff, but for defending the counter-attacks we had to work really hard, and that costs you a little bit of rhythm. They were always ready for the counter, they made it quite uncomfortable”.
However it’s a tactic he admitted won’t catch his side off guard again in the return leg. “Now we played the first game, we know more about each other, and now we go there and play again," he added.
Despite Klopp now being more prepared for his opponent should they deploy that same tactic, with Liverpool in a commanding position, the Portuguese side will be forced to come out and play - which may see Conceicao revert his side back to their traditional 4-4-2.
Although an equally compact shape as the 5-4-1 at Anfield, there will be more of an emphasis on attacking Liverpool - looking to utilise the dangerous Moussa Marega who looked lively at Anfield and was denied by two fine saves from Alisson.
As a result, Liverpool won’t be granted as much possession or time on the ball; however, with the return of Robertson, similar to last season, Liverpool could again expose the home side down both flanks whilst simultaneously allowing less space to be exploited in behind the defence.
The tie may not be over, but Liverpool remain in a great position to progress into the semi-finals on Wednesday night.
