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Why does Mauricio Pochettino play Levi Colwill at left back?

A tactical breakdown and explanation

Photo by Nigel French/Sportsphoto/Allstar via Getty Images

Roko Škrabić is the Chief Editor of Chelsea Croatia, home of the official Chelsea FC supporters group for Croatia, where this article originally appeared. He’s been kind enough to translate it for us. Be sure to give them a follow on Twitter.

Roko, whom you might also know as the “TheMightyGorgon” in the comments, is never shy of a strong opinion. Some of his previous contributions include analyzing Enzo Fernández’s game and Mauricio Pochettino’s strengths and weaknesses.

All visuals created with BuildLineup.

The question in the title has been one of the main question marks around our new head coach, and has been growing with each passing game. Indeed, why on earth do we have not one, not two, but three left backs on the bench, while Colwill the center back is playing in their position? It would be easy to conclude that Pochettino, at worst, simply doesn’t know what he’s doing, or at best, has an unfortunate tendency towards defensive football or a ‘defence first’ mentality even though our greatest issues clearly lay in attack...

... Or, you might not believe it, is there some kind of a tactical reasoning behind it all? – Actually, there is, and that’s what we will try to explain in this analysis.

Chelsea FC v Luton Town - Premier League Photo by Joe Prior/Visionhaus via Getty Images

For starters, it’s necessary to once again remind how obsolete formations have become. A deeper analysis of football is no longer done through common formations, ones you see on the TV before a match, or set up while playing Football Manager, but through different set ups of the same team in different phases of the game. As the phases switch, so do the player’s roles and positions on the pitch, both in absolute sense, and relative to their team mates. The formation you are served on the TV will usually correctly tell you only how the team will look like before the kick off.

Out of 4 main phases of the game (build up, attacking third, deep block, high press), a common formation like 4-3-3 or 4-4-2 will be most alike to the actual one in deep block. Also without the ball, but pressing high, a team’s formation will change to something relatively, or completely different. For example, in our last match vs Brighton, similarly to the rest of the season so far, we really did defend in a 4-2-3-1 as our team is usually shown on TV. However, when pressing high, the team’s formation changed to something more akin to a 4-4-2 where Palmer would press in the same line as Jackson:

Chelsea in deep (left) and high (right) block in the previous game vs Brighton.

With the ball the situation changes much more drastically. But not just in our team, but everywhere in modern football. Today practically everyone plays in a 5/5 split, which means that with the ball a team is split into 5 players who can attack the box, and 5 players who are predominantly tasked to stay behind and prevent counter-attacks (a more attacking variant is the 4/6 split, based on the same principles). Hence with the ball there’s no more of 4-3-3, 3-4-3, 4-4-2 or whatever. The only way a 5/5 split is differentiated is by basic geometry of the back and front 5; 3-2 or 2-3. Therefore, the formations, if we still insists on naming them, become 2-3-3-2, 2-3-2-3, 3-2-3-2, and the most popular one today, 3-2-2-3, or the ‘3-box-3’, how it’s often called.

examples of a 2-3-2-3 (left) and 3-2-2-3/3-box-3 (right)

As you can see, these have nothing to do with a 4-2-3-1 or such. This was the main reason why some were/are convinced we play with 3 at the back (a CB Colwill at LB was the other). Actually, we do play like that, but only with the ball. Without the ball, it’s a flat 4. Most big teams play like that nowadays. Take for example the greatest team of today, Pep Guardiola’s treble winning Man City. They normally defend with a line of 4, but as soon as they win the ball (back), one of the defenders (usually Stones) comes into midfield and along with the CDM, Rodri, forms a double pivot in front of the back 3. Mikel Arteta’s Arsenal does something similar, where their left back Zinchenko ‘inverts’ into the middle next to Rice or Partey.

last season’s City without the ball (4-3-3/4-5-1) and with the ball (3-2-2-3/3-box-3)
the most common Arsenal set ups without the ball (4-3-3/4-5-1) and with the ball (3-2-2-3/3-box-3)

And it’s not just Pep and Arteta. ‘Our guy’ Tuchel plays the same, minus the inverting FB. He has been building up attacks with a 3-2 his whole career, no matter if he set up with a 4 or a 3 at the back. As we know, at Chelsea he played a 3-4-3 where the ‘TV formation’ was very indicative of how the team was actually set up in both defending (5-4-1) and attacking (3-2-4-1) phase, which, as we have explained, is a rather rare exception nowadays.

The greatest difference between our beloved CL winning Chelsea team under Tuchel, and the (now also CL winning) City team under Guardiola, or even Arteta’s Arsenal, is the fact the lateral attacking players in Tuchel’s team were our full backs Chilwell and James, while Pep and Arteta have actual dribbling wingers in those positions, isolating them on the byline and at the same time not requiring them to fall back and join the back line when the teams loses the ball. As good and lethal as Chilwell and James were in those advanced positions, they do not possess the 1v1 dribbling skills, which is one of the main reasons why ultimately our attack became dull and stale. By inverting full backs, Pep, however, can have attacking, skilfull players like Grealish, Bernando Silva, Mahrez, or Jérémy Doku in those lateral attacking positions... It’s no wonder they’ve always been a goal machine, even before they got a literal goal machine to be their striker.

But, what’s all that got to do with Colwill? Hang with us just a bit longer. We have just explained why Pochettino insists on building up with a back line of 3, even if he defends with a 4. Actually, he’s been doing that his whole career, very similarly to Tuchel, and somewhat differently to Pep and Arteta with their inverted full backs. Tuchel and Poch like to play with ‘real’ full backs, but with the ball they instruct one of them to push high up, and the other to stay behind and help with the build up. At the same time, the winger on the advanced FB’s side tucks inside, forming a box midfield with the no. 10 and the double pivot, while the other winger stays on the byline to hold width on that side, since his FB remained behind to form a back 3 in possession. That way a planned assymetry is established, which you may have noticed in our team this season.

a typical Tuchel and Pochettino teams without the ball (left) and with it (right)

As the play progresses from the build up phase to the ending phase, the initially deeper FB may get the freedom and opportunity to overlap his winger, which then becoms a 4-6 split.

And here we arrive at this article’s question. In our team - why isn’t that player, the 3rd defender in the build up phase, a real full back such as Chilwell or Maatsen? Why does Colwill almost never roam high up or overlap his winger (except because he’s a center back)? You might have sensed the reason, and yes - it’s Thiago Silva. The following is the problem:

That is the wide unoccupied area of the pitch which is created with the defending formations 2-2 and 2-3 – an area which our legendary center back simply cannot deal with at his age. Just remember how Tuchel wouldn’t trust a then 36-year-old Silva in situation like these and always flanked him with two pacey center backs. Hence how could Poch trust him now, after he’s turned 39 the other day?

If it seems like all this was just an elaborate and unecessarily long way of saying „Thiago Silva“, don’t worry, it/he is not the only reason. In football today it’s become more or less accepted that 3-2 is the superior back 5 set up to 2-3. The reason again lays in those unoccupied wide spaces of the pitch which then become a fertile ground for opposition’s wingers to run into, creating dangerous counter-attacks which are the greatest weakness of big teams that all like to control games with possession, such as ours. Simply put, 3-2 defends those spaces much better than 2-3.

Don’t believe me? Just ask another great coach of today, Jürgen Klopp. Up until recently, he had consistently played 2-3 while pushing both his full backs up, tucking in both his wingers (Salah and Mané practically played as forwards since Firmino dropped deep as the false 9) and leaving all of the midfield 3 behind, giving them only an intermittent freedom of making that late run into the box.

the old Klopp’s Liverpool (2-3-3-2)

Somewhere in the second half of the last season, when nothing seemed to be working anymore, Klopp decided to try out a trick of his greatest rival, Guardiola. He switched to 3-2, left Robertson behind in the back 3 and inverted Alexander-Arnold into the midfield next to Fabinho (now Endo or Jones). By doing that, he achieved many positive effects, apart from the main one of defending the lateral spaces better; with the ball TAA becomes a midfielder, receiving an even better platform to perform his world class creative ability, great dribblers Salah and Díaz become isolated out wide against the opposition’s full backs, and the aging Virgil van Dyke is more often than not sorrounded by two defenders, becoming a modern version of a ‘libero’, a role that suits him perfectly (the same thing we’ve been doing with the even older Thiago Silva). Needless to say, after this change, Liverpool’s play and results improved drastically.

the new Klopp’s Liverpool (3-box-3)

Pochettino, unlike Klopp, didn’t have a recent eureka moment. He, as previously mentioned, has been playing 3-2 since the beginnings of his career in Espanyol and Southampton, while in the mean time, modern football theory and practice has (for the time being) approved the quality and the superiority of that strategy. And this is where we arrive to the second answer to the question in the title – now that we’ve established that Pochettino plays in a tactically modern and optimal way – it is clear (at most) one of his full back needs to play more advanced, while the other needs to stay behind. Or in other words, on one side we need a player who thrives higher up the pitch as a sort of a wing back, while on the other we need a player who’s good on the ball and can ably participate in the build up.

Out of our full backs, and we currently have five of them, which belong in the first, and which belong in the second category?

Chilwell, Maatsen and Gusto definitely in the first one. The vice-captain Chilly is very good in the defending aspects, however, he lacks on the ball qualities which are necessary in the build up. With the young ones, it’s other way around. Maatsen and Gusto are both very solid on the ball, but have spent the most of their careers as very advanced and attacking wing/full backs, and lacking experience, their defensive abilities are not yet developed to the point in which we could trust them in a back 3. Cucurella, on the other hand, belongs in the second category. Not so much because he’s a defensive monster, he clearly hasn’t been at Chelsea, but because his attacking abilities are very limited, so he shouldn’t ever be an advanced full back, while his only real qualities lie in his passing and distribution ability, which means we, and probably Cucurella himself, definitely prefer him to stay behind and help in the build up. The captain, James, is our only full back who excells in both roles (genuine world class). He’s equally brilliant high up the pitch and when staying behind, with the latter being the reason why Tuchel (and Potter) often used him as an RCB in a back 3.

So what happened when James got injured? – Gusto had to jump in. Considering the fact he’s a young, attacking full back which we obviously still don’t trust in a back 3 (even though he was solid playing there in preseason – it’s only preseason as they say), what kind of a full back did we require on the opposite side? – A defensive one. Therefore, we needed to play Cucurella... or – Colwill! Why Colwill? – Well, because Cucurella has been in bad form for a long time now (actually, pretty much ever since he arrived at Chelsea), consequently very low on confidence, and reportedly close to the exit door, while Colwill possesses all of his qualities (strong on the ball, good distribution, solid aerial ability) + many others, while he also, because of Thiago Silva, won’t be allowed to go forward too often anyway, so there’s wasn’t any upside to having a proper full back like Chilwell there.

our common set up without the ball (4-2-3-1) and with it (3-2-3-2) this season

Simply put, playing with two advanced full backs such as Gusto and Chilwell wasn’t wise and did not fit into the wider tactical set up. Why not play them both, push one higher up and keep the other one behind, you ask? – As previously explained, that latter role could simply be played better and safer by Colwill. All of it is even more pronounced when one of your center backs is Thiago Silva, next to which you especially don’t want a roaming, attacking full back. In short, considering the circumstances (James’ injury, remaining FBs’ profile, the tactical set up, Cucurella’s form and status, Thiago Silva) the Colwill at LB solution actually makes perfect sense.

What made, admittedly, slightly less sense was Chilwell left winger in front of Colwill left back. That actually sounds a lot worse than it is since the above explained assymetry actually gets them both in their natural roles of wing back (Chilwell’s best position) and left sided center back (Colwill played a whole season at Huddersfield there). Yet, this experiment left that side quite stale and was binned for good reason. In Pochettino’s defence, he did it after Nkunku’s injury and in an extreme lack of fit wingers (Madueke injured back then, Mudryk semi-injured and unfit to start, Palmer not yet signed). In support of that explanation, ever since Mudryk is fit, he has been regularly starting at left wing instead of Chilwell, which means this infamous experiment was nothing more than a forced adaption after all.

So what do we do in the next two games with Gusto suspended and James injured? Personally, prior to the Brighton match, I was convinced Gusto will simply be replaced by - Chilwell! One attacking full back for the other, while the rest of the defence switches to the right with Disasi playing as the defensive full back on the right side (a role he’s not unfamiliar with, having already played it in his career), and the wingers’ roles reversed. That would have looked something like this:

without the ball (left) / with the ball (right)

However, two things happened in the last match that have changed the situation. The first is another Chilwell’s injury (reportedly a month out at minimum), and the second is an unexpectedly excellent performance of Cucurella at right(!) back. There is, of course, a simple solution to just replace Chilwell with Maatsen and play on as shown above, but I don’t think that’s likely since Maatsen hasn’t yet been tried out in this position (not even in preseason), even though it’s his natural one. Apart from that, if Pochettino wants to install meritocracy in the team, he needs to reward Cucurella’s latest performance with a start. Also, Cucurella could actually provide us with an interesting and already mentioned tactical option to which Pochettino hasn’t yet been prone (neither was Klopp, up until recently) – the inverted full back!

it’s also possible for Cucurella to start on the left side; Colwill-Silva-Disasi would just move to the right, while the attacking set up would remain the same

Cucurella with his distribution and on the ball qualities seems tailor-made for an inverted full back. Also, his tendencies of aggressive front foot defending would actually get him into the space he was meant to occupy anyway, without leaving a huge gap behind him to be punished. This might just be the best (only) way for him to revive his Chelsea career and become worthy of the money that was invested in him (still unlikely, though).

Furthermore, this move would allow for all of Sterling, Palmer and Mudryk to start all at once (and without any of them being a false 9 in the place of the suspended Jackson), while also freeing Enzo to play in the double pivot, where many want to see him, and at the same time arrive in the final third as a part of the front five, which is obviously what both him and Poch want (with variable success so far).

Now it seems fitting to spare a moment to consider long term implications of this whole attacking/defending full back conundrum. You may have noticed some full back combinations are simply not viable in the current 4-at-the-back set up, especially not if Thiago Silva is playing. Specifically, with James on the opposite side we can have anyone, but he’s the only one like that. In combination with Gusto we can have Cucurella or Colwill, while in combination with Chilwell we can have (except James) Disasi or even Chalobah who also has some right back experience. Those combinations have a further effect on our choice of wingers, since some of them like to play wide (Mudryk, Madueke), while others prefer to tuck into the half space and play as no. 10s (Nkunku, Palmer). Here, similarly to James, Sterling (and apparently Palmer too, but we haven’t witnessed that yet) is the only one to be able to play both roles, although when tucking in he prefers to become another forward, and not a 10. Considering all that, the following two options will likely be Poch’s great dilemma this season:

option A without the ball (left) and with it (right)
option B without the ball (left) and with it (right)

Here we can see, among other things, what many fans have already noticed – Chilwell and Mudryk, in this moment, are not a good combination on that left side, nor will they be until Chilly improves in the deeper role, or Mudryk in the more central role (such as Nkunku, for example). Their current style and preferences put them both in the same wide space in the attacking phase.

In theory, there’s also an option C, if Poch too decides to use Pep’s inverted full back trick, like Arteta and Klopp have done to great success. Apart from the already discussed Cucurella, another one of our full backs could play that role, and that is, of course, James (that man can play anywhere). Personally, I like this option the most since it would, as previously explained, elegantly allow Enzo to be both in the double pivot and in the attacking 5 (or 6). However, we will not dwell on Enzo this time, that is one rabbit hole that probably deserves an analysis of its own...

option C without the ball (left) and with it (right)


  1. Pochettino’s Chelsea play a modern and positionally optimal football, similar to other big teams with great coaches of today.
  2. Colwill at left back is a logical solution to the circumstances (James’ injury, remaining FBs’ profile, the tactical setup, Cucurella’s form and status, Thiago Silva) and we will likely keep seeing it.
  3. The presence of Thiago Silva is a further strong reason why we cannot even think about playing with two attacking full backs (ex. Chilwell and Gusto).
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