The difference between the first and second half of Liverpool's UEFA Super Cup date with Chelsea was telling.

In the first half, something felt wrong when Liverpool were in possession of the ball, their attacking movements unbalanced and the Reds struggling to achieve clean progression of the ball in the midfield area against an N’Golo Kante led Chelsea side. In the second half, everything looked sharper with the ball moving more freely. The catalyst between these changes was the introduction at half-time of Roberto Firmino, and this only served to further highlight the issues that Liverpool may have with replacing him when injured or in need of a rest.

Firmino acts as the conduit through which the ball flows for Liverpool, but in the first half of Wednesday’s match, a potential replacement from Jurgen Klopp was offered in the form of Sadio Mane. Mane played there, at times, last season; in terms of pure quality, the switching of Mane and Firmino is not a downgrade in terms of quality.

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But the difference in style and identity between the two though does lead to a change in the playing style for Liverpool. While Firmino is most comfortable dropping deep as the ‘9’ to collect possession and allow the left-sided and right-sided attackers to move centrally, Mane constantly sought to find angles to run in behind the defensive line to stretch the Chelsea defence and force their block deep.

This change of approach is not necessarily negative. Indeed, against teams that leave space behind their defensive line, the constant vertical threat from Mane in a central position should be enough to create space for the central midfielders for Liverpool; it would allow them to move into more advanced and creative positions. The change of forward from Firmino to Mane simply means that the rest of the attacking structure has to change in order to compensate for their very different skill sets.

Perhaps more concerning, however, is the fact that moving Mane into the centre of the field takes him away from his position on the left of the attack, a position that the Senegalese attacker has all but perfected over the last couple of seasons under Klopp. His former club Southampton have become the latest to know about the havoc he can cause in that role, putting in a man-of-the-match performance and scoring a superb goal in the 2-1 win at St Mary's.

But what does Mane bring as a '9', and how much do Liverpool miss him when not in his regular left-sided position of the front three?

The above heat map shows the positioning of Mane over the course of the 2018/19 season; data from 2019/20 is not used, as the sample size would be too small to be effective. Last season, Mane played predominantly on the left side of the three man attack. This does not show the full picture though, as Mane is more likely to drift into the half-space or the central area as Liverpool enter into their attacking phase.

Interestingly, something similar has emerged in the Premier League already this season from Manchester United. Ole Gunnar Solskjaer has used Marcus Rashford in a similar role and Solskjaer has stated in the media that he expects Rashford to be occupying central areas more than the left side of the pitch.

Imitation is after all the most sincere form of flattery.

It was interesting that the switch of Mane from the left to the centre lasted for just 45 minutes in Istanbul against Chelsea, when he was switched back to the left side following the introduction of Firmino as a substitute. This is unlikely to have been a direct reflection of the performance of Mane, and instead a sign of the need to introduce the Brazilian as a creative force.

What was clear though was that the presence of Mane centrally changed the overall tactical structure of Liverpool quite dramatically. While Firmino prefers to drop from the forward line into the ‘10’ position to link the play we saw Mane constantly looking for opportunities to run in behind the Chelsea defence on the blind side of the central defenders.

In situations like this with Firmino as a ‘9’ he would tend to hold his position in order to allow the ball to be played into central positions. This would then create an advanced platform from which the rest of the Liverpool attack would be built. Mane, on the other hand, is a player who relies on his speed and timing to make runs behind the opposition defence. What is interesting is that these runs tended to be made on defenders on their blind side.

As the right-sided defender is concentrating on the ball Mane would make a quick vertical run behind him. This is a good move if the ball can be played into that area to release Mane through on goal, but if that pass is not on, then the vertical run can still be effective. It will force the defenders to drop deeper and this will create space between the opposition midfield and defence, meaning the two central midfielders for Liverpool have to be willing to move higher to occupy these spaces.

The desire from Mane to run in behind the defensive line is a natural part of his game. When playing from the left side the threat he poses when running through the gap between the opposition right back and central defender is a key part of Liverpool’s attacking threat.

The only issue with Mane making these runs from central areas is that there is no link player occupying the space he is leaving behind in order to progress the ball more gradually towards the penalty area.

A large part of squad building in the modern game is achieving the correct balance in your squad to ensure that you can be tactically flexible from game to game. You may carry two left wingers in the squad, for example, with one preferring to stay wide and attack the outside while the other drifts inside towards the central areas.

This allows you to make changes easily from game to game. While having tactical versatility can be important it is also essential that a coach understands the implications of moving a player from one position to another. This has to be the case for Klopp when he moves Mane.

Playing predominantly from the left of the attack over the course of the 2018/19 season, Mane scored 26 goals from 21.91xG. This level of output shows how important Mane was to Liverpool when playing from that position out on the left-hand side. If he is taken from there and moved centrally, there are no guarantee he will be as effective in terms of his goal output.

Playing from the left side with another player, usually Firmino, as the ‘9’ in the central area allows Mane more freedom to occupy space across the attacking line and make his vertical runs in areas that really hurt the opposition. The image above shows this as the ball is on the right-hand side of the field, and the opposition defenders are all attracted over to engage with the ball carrier.

In these moments of transition, when the opposition defensive block is not set, the pace of Mane can be essential when Liverpool look to access space behind the defensive line or on the other side of the pitch.

Against sides that sit in a deep defensive block, Mane has an impact with his ability to find and exploit pockets of space. He is capable of collecting possession of the ball in deeper areas of the half-spaces, and then connecting with more advanced areas. As the ball is passed into these forward players, the effectiveness of Mane is evident as he isolates defensive players and makes vertical runs in between their positions.

This pace against a side in a deep defensive block can cause confusion in the opposition, and create spaces that others can move into.

These positions, in the half-spaces between the wide and central areas, can cause chaos for the opposition. As Mane receives the ball in these areas he forces the opposition defenders to make a hard choice. Do they move out to engage the ball or sit in their shape and allow Mane to receive and turn in dangerous spaces? This is shown in the previous image. Should the Chelsea right-back or right-sided central defender step out to engage Mane, they will leave another Liverpool player free to be played in behind the defensive line.

The first-choice front three for Liverpool - Mohamed Salah on the right, Firmino centrally, and Mane on the left - tend to play in a relatively compact shape in build-up play. The two wide forwards will tuck inside and allow Firmino to adopt deeper positions, and their movement into the narrow shape will empty the wide areas for the fullbacks to advance into.

These movements are well-rehearsed and very difficult for the opposition to combat. If Mane is replaced with another player, Divock Origi for example, then the overall structure for Liverpool becomes very different. The Belgian has shown more of a willingness this season to hold the wide position and this has a knock on effect for the left-back, who has to move higher, and the left sided central midfielder who has to fill a space in the half-space. These movements in turn alter the movements and positions of other players.

It would be incredibly unfair to label the use of Mane centrally against Chelsea as a failure; he has featured there before and proven successful at it, most notably in the 5-0 win against Watford at Anfield in March.

The game state ultimately forced the change from Klopp and the introduction of Firmino saw the Liverpool attack, including Mane, come alive.

The simple truth is that there will be spells over the course of the season where Firmino will either be injured or banned or even just in need of a rest. The need for an alternative in these instances may well see Klopp turn again to Mane to play through the middle.

If this is the case again then close attention should be given to to the way that Liverpool attack.