In The Zone: UEFA Champions League group stage review

The 2021/22 UEFA Champions League group stage ended with six straight wins for each of Ajax, Bayern München and Liverpool, Barcelona’s first early exit in 20 years, and ten goals from a striker entirely new to the competition – Ajax’s Sébastian Haller.

If those are some of the stand-out numbers, the job of analysing the action falls to UEFA’s team of technical observers who met after the group stage concluded to discuss their tactical and technical findings from this opening phase. This was the first season in which an observer had been assigned to each of the 96 group-stage matches and the observers' wide-ranging, illuminating discussion touched on such topics as tactical flexibility, high pressing, creative centre-backs, and the use of rotations and movement to create space.

Adaptability and identity

On the question of flexibility, only ten teams played with the same formation throughout the group stage and UEFA's observers noted how sides changed shape in and out of possession as well as switching formations mid-game to adapt to the opposition. Elaborating on this point, Roberto Martínez, the Belgium national-team coach, said: "You see teams play a different system on the ball and different system off it."

Martínez cited the case of Benfica in their home match against Bayern München, observing how when pressing Bayern in the opposition half, one of the Portuguese side’s three centre-backs would step up to man-mark one of the Bayern players. Defending in their own half, though, the centre-backs remained together in their defensive unit as Benfica’s 3-4-3 morphed into a 5-4-1.

If players today are accustomed to these adjustments, Zvonimir Boban, the UEFA chief of football, highlighted the need to marry flexibility with a clear identity: "We have noticed that despite a trend of frequent tactical changes throughout the season, and often even during the match itself, the most successful teams were again the ones with the clear vision and tactical identity.

"The players are requested to adapt to multiple positional tasks throughout the season - what used to be an exception is now becoming a standard and, I dare to say, not a good one. This overload prohibits the players from being comfortable on the pitch and optimally expressing their qualities.

"For a team to grow, it is fundamental to have a basic system and put players in the proper positions that fit their skills and qualities, and allow them the time and continuity to bond with their teammates on the pitch. And this, unfortunately for many teams, is not the occurrence in football today."

Pressing matters

Pressing has been a key tactical element for some seasons now and the consensus among UEFA's observers is that teams are increasingly well prepared – physically and tactically – when it comes to getting into good positions to press the ball high up the pitch as their opponents build from the back. "When the opposition goalkeeper has the ball, you see high pressing and good positions, making it difficult for the opposition," said Mixu Paatelainen, adding that the fact that many teams continue to try building from the back "has led to many mistakes and scoring opportunities".

When it comes to pressing from open play, Martínez highlighted the work of Liverpool and Manchester City, saying that "the synchronisation with the way they stop the internal pass and the way they apply pressure is fantastic". The PPDA (Opposition Passes Per Defensive Action) metric for measuring pressing intensity shows that Ajax (7.52) and Liverpool (7.74), two of the three sides with a 100% record, pressed with the greatest intensity in the group stage. Another team who pressed to impressive effect were Salzburg (8.12), their high-intensity approach earning them a place in the UEFA Champions League knockout stage for the first time as one of four teams from outside the five highest-ranked leagues to advance (along with Ajax, Benfica and Sporting).

Willi Ruttensteiner, the Austrian observer and Israel national-team coach, praised Salzburg for an approach applied at every level of their club. "They played this same style, this same philosophy, as they do in the Austrian league – they pressed immediately high and played as deep as possible after winning the ball and played with high intensity all over the game," he said. "I thought they’d adapt a little for the Champions League but the coach [Matthias Jaissle] said, 'No, we have our philosophy' and they succeeded."

Three at the back

One major talking point from the UEFA EURO 2020 technical report was that 15 of the 24 participating teams played with three at the back at some stage of last summer's final tournament. During this autumn's group stage there were nine teams who began matches with three centre-backs while others – such as Ajax, switching mid-game to a 3-4-3 – used a back three at least once during the course of a match.

Chelsea, the reigning champions who set up habitually in a 3-4-2-1, caught the observers' attention for the way their outside centre-backs – César Azpilicueta and Antonio Rüdiger – would step forward to support attacks. Indeed Rüdiger and fellow centre-back Andreas Christensen ranked among the top seven for ball carries among central defenders in the group stage – with 64 and 71 respectively.

"If you let them go up, someone else should take over in defence," said Peter Rudbæk, which in Chelsea's case invariably means Jorginho. For another view of the extent of centre-back creativity, Packie Bonner said he saw "centre-backs stepping into the opposition half, being able to play that penetrating pass but then reverting to defensive duty very quickly". Additionally, he wondered whether less well-resourced teams suffered for the absence of a naturally left-sided centre-back to provide balance.

Create the space

It was common throughout the group stage to see rotations involving wide players and full-backs as teams looked to unlock well-organised defences but there were other notable ploys to make space. A feature of Ajax's efforts in winning Group C was their flexible positional play, with more than one observer pointing to the way their midfield three excelled at getting free through rotations.

Group A winners Manchester City were strong in this area too with Robbie Keane highlighting their work in the "half-spaces". He said: "Man City are probably the best at doing it – in the half-spaces, in the pockets, in between the lines. They're brilliant at getting either side of the opposition midfield players." With clever creators like Kevin De Bruyne and Bernardo Silva, he explained, City get either side of the opposition pivots and look for overloads with the wide attackers out on the touchline.

From City, the use of the inverted full-back was evident too, though Martínez explained that this was a defensive measure first and foremost. "Sometimes we think the inverted full-back is to give the extra line of pass but it is not – it is to be ready if you lose the ball as you can defend the ball quicker in a central area and stop the opposition." For a team not in control of a game, though, the inverted full-back can lead to difficulties: Shakhtar Donetsk used this tactic against Real Madrid but, as one observer noted, were left exposed down the sides of the centre-halves.