This is a post in the philosophy of soccer series. See the introductory post here.
Ball possession statistics in soccer are used as an informal measure of the relative dominance of the two teams in a given match. This is usually expressed as a percentage, e.g. Juventus 38%, Barcelona 62% (indicating that Barcelona had much more of the ball). Fifa also uses the word “possession” in their current (2014/2015) version of the Laws of the Game. The word appears to be used by them interchangeably with the phrase “control of the ball”. See the following passage, for instance, from page 120:
A goalkeeper is not permitted to touch the ball with his hand inside his own penalty area in the following circumstances:
- if he handles the ball again after it has been released from his possession and has not touched any other player:
- the goalkeeper is considered to be in control of the ball by touching it with any part of his hands or arms except if the ball rebounds accidentally from him, e.g. after he has made a save
- possession of the ball includes the goalkeeper deliberately parrying the ball
Fifa do not provide a formal definition of what possession is, but the passage above implies that it is conditional on the player being in physical contact with the ball: a player takes possession of the ball at the very moment of deliberately making contact with it. But that would seem to give too limited an account of what possession is. The passage also mentions that a goalkeeper (and presumably any other player) can release “the ball from his possession”. At what point, precisely, are we to say that the ball has been released from the goalkeeper’s possession? Goalkeepers often bounce the ball off the turf but are never then penalized for handling the ball a second time. And what happens after the ball is released to a teammate: who, if anyone, is in possession of the ball in the time between the goalkeeper’s releasing the ball and the next player’s making contact with it? If we want to understand what “possession” in fact means, in its common usage, then the Laws cannot be our guide.
Discerning who is in possession of the ball at a given moment might seem intuitively straightforward. And yet it is surprisingly difficult to pin down in formal language just what it is that allows us to say that this particular player has possession of the ball. In practice, the ball does not have to be in physical contact with the player for us to recognize possession (a goalkeeper might hold the ball in her gloves for a few seconds, but an outfield player is never normally in prolonged physical contact with the ball), nor, as we’ll see below, does the player necessarily need to be spatially closer to the ball than any of the player’s opponents are at a given moment.
Revealingly, this lack of formal clarity has given rise to a disagreement about how possession should be measured as a statistic. This disagreement is described in a piece in Slate by the writer Hana Glaser. The traditional way of measuring possession is known as the chess clock method. This requires that there is someone in a back room manually keeping track of which team is in possession at any given moment. This person, Glaser notes, is “armed with a three-button timing mechanism. One button corresponds to Team A having possession, a second corresponds to Team B having possession, and a third is pressed when the ball is out of play.”
The soccer stats company Opta Sports uses a rather different method. They claim that the chess clock method is too untrustworthy because it is “reliant on the person logging the data remembering to hit the button [while] the person doing it usually has other tasks to perform and other data to log.” Opta’s alternative measure is derived from the number of passes made by each team. A team’s possession percentage is calculated as the number of completed passes made by that team over the course of the game divided by the total number of completed passes by both teams. But, of course, this is not actually a measure of possession at all. An attacking team could make fifteen passes in fifteen seconds before losing the ball to the opposing goalkeeper, who then holds onto the ball for another fifteen seconds before passing it to a teammate. On the traditional way of counting it, the two teams have had equal amounts of possession. Opta’s method says that the attacking team have had 15 times more of it. For this reason, Glaser notes that Opta’s method should not be named “possession” at all, but should be given a different name, such as “pass volume” or “dominance”.
The disagreement here appears to arise from a lack of clarity about just what possession is to begin with. Glaser calls possession a “subjective statistic”. Opta’s method tries to eliminate this perceived subjectivity by assuming that possession has something to do with how many touches a team’s players make on the ball. But this leaves out the dimension of time. Glaser quotes the soccer writer Chris Anderson saying that the player in possession is simply the one who is “temporarily closer to the ball than the other guy”. But this, too, is inadequate. To see why this is so, let us consider the through-ball.
Who has possession during a through-ball?
A through-ball is a pass that is played through a gap between two opponents into the path of a teammate. A feature of through-balls is that, as the ball travels through the gap, it can, momentarily, be spatially closer to one or both of the defenders than it is to the passer’s teammate who is the intended recipient. Nevertheless, if the pass is well-executed it is the passer’s teammate who gets to the ball first.
This is best illustrated through video, of course, so here are some clips of through-balls.
The first is by Nigeria against Sweden in the 2015 Women’s World Cup (see on youtube; starts at 1:40).
The second is by Arsenal against Liverpool in an FA Cup match from February 2014. See the two passes in the build-up to the goal here. These are actually two through-balls played in quick succession, between the same two defenders (although the second pass is played in the direction going away from the opponents’ goal, so would perhaps be better labelled a reverse through-ball).
So what’s going on here in terms of possession? If possession is really just about being “temporarily closer to the ball than the other guy”, then we would have to say that possession changes hands twice over the course of the manoeuvre: the ball starts off in the possession of the passer, momentarily enters into the possession of the opposing defenders, and ultimately ends up in the possession of the passer’s teammate. But that can’t be right. The beauty of this type of pass, surely, lies precisely in the fact that the defending team is never able to take possession. The defenders not only fail to touch the ball, they never even have a chance of touching it. And, moreover, there’s another phrase in existence which suggests that this analysis is wrong. When a defender does in fact manage to intercept the ball in a pass like this, the commentator is likely to say that the defender has “stolen” the ball. The implication is that the defender had no right to the ball to begin with—the ball was not in the defender’s possession simply by virtue of the defender’s proximity to it; in order to take possession, the defender had to actively seize it.
Perhaps no-one is in possession of the ball as it passes through the gap? This would be an odd conclusion to make: first team A has it, then nobody has it, then team A has it again? This, again, does not sit well with commentators’ use of the word “stolen”: if no-one owns something, it can’t be theft for team B to take it. Once again, this analysis can’t be right.
What we do know is that the pass is intended for a specific teammate. The most natural thing to say, then, is that possession changes hands just once, between the passer and the recipient. The ball is in possession of team A throughout.
But how can we capture this formally, without throwing our hands up and declaring it all to be just so subjective?
So what is possession?
There is a simple way to resolve all of this, which is to say that the player who is in possession is the player who is best positioned to make the next touch on the ball. To be best positioned to make the next touch is not necessarily to be closest to the ball at a given moment. Rather, it means that you will get to the ball first, if you only move towards it appropriately. And neither is it necessary to actually see into the future in order to say which player in fact is the best positioned. It is, rather, a matter of taking account of the prospective path of the ball and of each of the players: In which direction is their momentum taking them? Do they need to accelerate in the direction of the ball? How fast can they run?
On this formulation, team possession is a simple aggregation of individual possession. A passing player “releases possession” of the ball at the moment that they strike it, propelling the ball away such that they are no longer the player best positioned to make the next touch. And possession changes hands between teammates at this moment too: as soon as the ball is kicked, it becomes the “recipient’s ball”.
It might seem odd to say that the recipient of a pass takes possession of the ball as soon as the passer kicks it. And perhaps it is. I’m going to maintain, however, that this formulation better captures the concept of possession as it is used than any of the alternatives on offer. It allows us to escape from the conclusion that possession is merely subjective. There is a fact of the matter about who is best placed to next touch the ball, and it is this that we are really concerned with when we talk about possession. The most important touch is always the next one.
The difficulty here is not that possession is subjective, but that in practice it is difficult to measure. Often the ball will follow a path midway between two players. Here, the truth about who is best positioned to get to the ball first is largely dependent upon the players’ current momentum, and this is a matter of the internal dynamics of each player’s body. It may not be immediately visible, either to an observer or to the players themselves, just which of the two players has the advantage. But this is true of any perceptual task. Perception does not occur in momentary snapshots but is extended in time. For the players themselves the act of attempting to run towards the ball is an essential part of the process of perceiving whether they can get there first. Perception is not something that just happens to us but something that we must actively do, and sometimes it is necessary to act in order to generate further information in order to perceive. For the observer, likewise, if it is initially unclear who will make the next touch, then it is necessary to continue to watch the action unfold.
Why does any of this matter?
The above might seem like a lot of unnecessary fuss to make over what is after all just a single word used in talking about an ultimately trivial game. And I suppose it is. But I’ve dwelt on it at such length for a reason. The concept of possession is representative of a much larger class of concepts that we use when talking about collective activities and which carry with them a good deal of confusion because they are invoked ambiguously at both the individual and the collective level. The temptation for researchers, when faced with such an ordinary-language muddle, is to simply eliminate the problem by fiat. We could simply stipulate that possession will be understood only as an abstract measure applied to the team. Or, as in the Laws of the Game, we could try to use it in a very restricted sense to refer to an individual’s making contact with the ball. Or we could simply proscribe any mention of the word altogether.
But to do so would, I believe, be to sell ourselves short. The concept of possession really does play a role in explaining how the game is played. An appropriate understanding of concepts like this will be necessary if we wish to understand how a soccer team works, and a similar analysis will apply to analogous concepts in other arenas in which individual actors collaborate towards a common end.
Possession is a future-oriented concept. The player in possession is the player who is best positioned to make the next touch on the ball. The possession statistic attributed to the team is really an aggregation of time-in-possession for each of the team’s players. There has been some confusion over the concept of possession arising from the fact that it is used both in a narrow sense, to denote a particular player’s making contact with the ball, and in a broader sense, as a simple percentage denoting the team’s dominance over the course of the game. This confusion has led to the suggestion that the latter figure is nothing more than a “subjective statistic”. The team’s possession is not actually a subjective matter. But in order to see this clearly it is necessary to apply some formal reasoning. What is important, if we wish to resolve the confusion between the levels of team and individual, is that the team’s possession must be expressible in terms of individual players’ possession. The formulation outlined here, attributing possession to the player best positioned to make the next touch, satisfies this criterion. And furthermore it makes clear that possession is not a static thing, but is relational, shifting over time along with the positions of the ball and the players on the pitch.