Introducing the Zero-Point – Part 2
In the first part of this article, we have analyzed the game action Outside Positioning down to the details, and theorized that there is a perfect position to receive the ball in order to be able to play progressive passes: the zero-point. In the second part, we will try to prove whether this theoretically perfect position actually exists, and if it helps players to play progressively, using StatsBomb’s 360 data from the UEFA EURO 2020.
Written by: Mats de Leeuw den Bouter, co-founder Impact Performance Coaching
Now that we’ve established that a zero-point should be a good starting point to play progressive passes, let’s find out if it actually works! Using StatsBomb’s publicly available 360 data, we can find zero-points and analyze if central defenders who are positioned in zero-points play more progressive passes than players who are not in a zero-point.
First, we need to use the data to find the moments when a central defender is performing the Game Action Outside Positioning. We did that by searching for all instances where a central defenders received the ball from a teammate. Before receiving the ball from a teammate, players can always adjust their position to get better conditions to be able to play forward. Outside Positioning actually occurs more often than only these moments (players don’t always get the ball when they are asking for it), but we can only compare outcomes for the moments where the player actually receives the ball. During the entire EURO2020 tournament, there were 12.291 instances that a central defender received the ball from a teammate!
For all these moments we can construct match frames. With these match frames we can see where all players who were visible on the tv footage were positioned.
As you can see, there are only six visible players from Austria, and four from Italy. The other players were not on the screen at the moment that Martin Hinteregger received the ball. But we don’t need their position to find the zero-point for Hinteregger.
To answer our research question, we will first have to clean the dataset. After we only have the relevant ball receipts of central defenders, we still need to define the zero-point and progressiveness in a quantitative way, so we can determine for each ball receipt whether the central defender was in a zero-point and whether he followed this ball receipt up with a progressive action. In the next part of this article, I will explain how we did all this, so the next section is a bit technical. If you want to skip right on to the results (I won’t judge you), click here!
Cleaning the dataset
Because we are only interested in moments where the central defender is performing Outside Positioning, the first step is only selecting the moments where the on-ball player is outside the opponents’ defensive block. To that end, we need to define the opponents’ defensive block.
The defensive block is defined as a convex hull of all defending outfield players. To construct a convex hull, we need to know the location of at least three defensive players. We can exclude all instances where there are less than three defenders on camera, which happened 344 times during the entire EURO2020. In Hinteregger’s example we know the location of four of Italy’s players, so we can make (a part of) the defensive block.
To find the zero-point, we don’t need to see the entire defensive block. We just need to see the part of the block that is between the on-ball player and the most valuable space. If the line from the on-ball player towards the most valuable space intersects the part of the block we can see, we can determine whether the on-ball player was in a zero-point. If the line doesn’t intersect the convex hull, we can’t be sure whether the player was in a zero-point or not, so we have to exclude those moments. That happened 463 times in the entire dataset.
Other moments that got excluded:
– Moments where the on-ball player was not on screen, or there was a close-up so that no opponents were visible: 933 times.
– Moments where the on-ball player was inside the defensive block instead of outside: 122 times.
– Moments where the on-ball player was farther than 1.5 times the width of the gap away from the gap: 142 times. We excluded these because in these moments the opponents usually wouldn’t try to press at all, but rather just sit back.
– Moments where the on-ball player was in the attacking third: 484 moments. We excluded these moments because often the situation was no longer considered build-up, and were sometimes following a corner or a free kick.
– Moments there was no pass following the ball receipt: 508 times. These included moments where the central defender lost possession in a dribble or a duel, but, for example, also moments where the referee blew the whistle for half- or full-time.
– Moments where the following pass was incomplete: 957 times. We did this because we needed to compare the results of the passes, and we can only do that if we compare successful passes.
That leaves us with 8.715 moments where a central defender receives the ball in a build-up situation, and plays a successful pass after receiving. At all these moments, we know the location of at least three opponents, and the line from the on-ball player towards the most valuable space intersects with the defensive block. That means we can determine whether the central defender was in a zero-point for all these moments!
Defining the zero-point
The idea of the zero point is that the on-ball player can reach the most valuable space as easily as possible. There shouldn’t be an opponent directly in the line between the on-ball player and the most valuable space. Ideally, the on-ball player would be positioned perpendicular to the gap between two opponents. For more theory on the zero-point, see our previous blog.
For each of the 8.715 moments we need to determine which gap is the gap the zero-point should be calculated for. That is the gap that intersects with the line between the on ball player and the most valuable space. The on-ball player should position himself in relation to this gap to play towards the most valuable space as easily as possible. That’s not necessarily the same as the gap with the two closest opponents, as you can see in the example below.
Even though Finland’s two attackers are closest to Jason Denayer, the line to the most valuable space intersects with the convex hull in the gap between Finland’s attacker and left fullback. This makes it the most valuable gap, and therefore the zero-point will be determined for that gap.
For every gap, there are multiple positions that would qualify as a zero point. For example, every point on the line perpendicular to the gap is a zero point, because then the distances towards both opponents are exactly equal. The length of this perpendicular line (altitude) was set at 1.5 times the width of the gap for this research.
But it’s not as if a position half a meter from this altitude would directly mean that the player is no longer in a zero-point. He would still be able to play towards the most valuable space with relative ease.
For example, Elvedi is not directly on the altitude of the gap, but the gap towards the most valuable space is still very much open for him. To determine when the gap is no longer open for the on-ball player, we randomly selected 100 of the 8.715 moments to qualitatively analyze the player’s positioning using video-analysis. From this sample we discovered that if you were positioned between one third and two thirds of the gap, you still had a decent chance of playing through the gap. Any more to the side, and you would quickly get pressed by one of the two opponents. So to determine the zone in which the on-ball player would be in a zero-point, we drew lines between the most valuable space and the points on one and two thirds of the gap.
The points where this funnel towards the most valuable intersect with the triangle formed by the gap are the points that enclose the zero-point zone. So the zero-point zone for this particular ball receipt would be as follows:
We believe that in this situation, a player would be in a zero-point if he were located within the green shape. Using this same method we can determine the zero-point zone for all 8.715 ball receipts of all center backs at the EURO2020. A few examples:
Defining progressive actions
For this research we defined progressive actions as actions that ended at least 15% closer to the opponents goal than they started. The start location was defined as the location of the ball receipt, and the end location as the end location of the pass that followed the receipt. The pass itself did not necessarily have to be a progressive pass for the action to be a progressive action. If the central defender carried the ball 15% closer to goal first and then made a short sideways pass, the action was also deemed progressive.
The only exception to the 15%-rule was if the end location of the action was lower on the field than the highest opponent was at the moment of the ball receipt. This was done because in some situations the algorithm would deem passes progressive that really weren’t. This often happened when the ball was low on the field, when the opponents weren’t pressing and the gap was quite wide. If the central defender then passed the ball to a midfielder who dropped out of midfield (just below the defensive block), it was often considered a progressive pass even though it was a really easy pass that didn’t affect the chances of creating a chance at all. Check out the clip below for an example.
Let’s quickly summarize the previous paragraphs for the people who skipped this section:
– We removed all irrelevant ball receipts, and now we are left with 8.715 ball receipts where we can determine whether the central defender was in a zero-point, and whether he followed up this ball receipt with a progressive action.
– The zero-point was defined as a zone relative to the gap between the two opponents and the most valuable space. If you are positioned in this zone, it would theoretically be easier to play towards the most valuable space.
– Progressive actions were defined as actions that brought the ball at least 15% closer to the opponents’ goal, and was played past at least one opponent.
Time to find out if positioning in a zero-point helps central defenders to play more progressive passes! Out of the 8.715 ball receipts we analyzed, the central defender was in a zero-point 2.529 times, just short of 30% of all moments.
Of the 2.529 moments the central defender was in a zero-point, they made a progressive action 850 times, which is in 34% of cases.
And of the 6.186 moments the on-ball player was not in a zero-point, only 21% of the following actions were progressive. Using a Chi-square test*, we found that central defenders in a zero-point performed significantly more progressive actions than central defenders not in a zero-point (X2 (1, N = 8715) = 159.2, p < .001).
That means that by positioning yourself in a zero point as a central defender, you can increase your chances of performing a progressive action by more than 60%!
That’s a pretty big jump. Being able to play more passes towards goal is very important, especially in a game where goals are relatively rare and therefore extremely valuable. In the Top 5 Leagues last season, there was a close relationship between goals and progressive passes. It’s hard to prove that more progressive passes from central defenders will directly result in more goals, but it’s also hard to argue that central defenders playing more progressive passes wouldn’t contribute to creating more goal-scoring opportunities.
Also only 21% of passes were backwards when a player was in a zero-point, compared to 29% of passes from players not in a zero-point.
One could think that because players in a zero-point plays more progressive passes (which are generally more difficult passes than passes to the side or backwards passes), the pass accuracy from zero-points could possibly be lower because of the increased inherent difficulty. However, the pass accuracy for players in a zero-point and players not in a zero-point is nearly identical, with 93% for both categories.
Players who are in a zero-point won on average 8.4 meters towards the opponents goal, whereas players who weren’t in a zero-point won only 4.8 meters for their team. That’s almost double the distance! This difference was also found to be statistically significant using an independent samples t-test**, t(8714) = 12.3, p < 0.001.
So central defenders in a zero-point play more progressive passes, fewer backwards passes, and win almost double the distance towards goal compared to central defenders not in a zero-point. All this while not losing any more balls than players not in a zero-point would. Is the zero-point one of the most powerful concepts in football tactics?
Check out the video below for some more examples of positioning in a zero-point and the actions that follow:
The advantages of positioning in a zero-point almost sounds too good to be true, but it could possibly be even better. Almost all of the moments where the central defender was in a zero-point during EURO2020, they didn’t seem to be actively aware of it. It just happened, and it afforded them progressive options. Some players seemed to be consciously taking up positions that resemble a zero-point, but the overwhelming majority of positioning in zero-points is accidental.
If central defenders would know that being positioned in a zero-point would increase their chances of playing progressive passes, they would probably start looking for these zero-points more often. Keep in mind that only thirty percent of all ball receipts were in a zero-point. There’s so much room for improvement in this aspect of football. When players are continuously and actively looking for optimal positions (ie. zero-points) during build-up, they are automatically more focused towards the most valuable space and the progressive options these zero-points afford them.
When a player is not aware that he is in a zero-point, he might not even realize he has the option to play progressively. It happens too often that a central defender has the ball in a perfect position, with an open pass-line towards one of the midfielders or strikers, but chooses to pass it towards the full-back or back to the other central defender. Personally, I think it’s one of the most frustrating moments as a spectator during a match.
But when a player is aware he is in a zero-point, he will always look for the progressive option. In a zero-point, you will always have the space between the two opponents open to play through at the moment of receiving the ball. Having this option through the gap will either force one of the opponents to close this line towards the most valuable space (which will result in more space for a teammate next to you), press you from a suboptimal location (practically forcing you towards the most valuable space), or create enough uncertainty in the opponents that you don’t get pressure at all (which gives you more time and also leaves the gap open). Nothing but upside!
Zero-points are one of the tactical concepts we work on with the players we coach. And zero-points are not only for central defenders! Actually, all positions in football benefit from good positioning in relation to opponents and the most valuable space at that moment. So while the execution of perfect positioning may vary between central defenders and wingers, the same principle applies: Before getting the ball, try to find the position that gives you the best conditions to play towards the most valuable space.
We aim to release more of these articles and also online courses about the tactical concepts we usually only give to the players we work with. Please let us know what you would find interesting to learn!
*The Chi-square test compares the observed frequency of progressive actions with the expected frequency based on the assumption that they would be equal if positioning in a zero-point would not increase your chances of playing progressively. Click here for more information about Pearson’s Chi-squared test.
**The t-test can be used, for example, to determine if the means of two sets of data are significantly different from each other. Click here fore more information about t-tests.