The science of shirt numbers

Yesterday, Michael Cox, author of the Zonal Marking blog and The Mixer, tweeted:

Now, there is some science to how football shirts are numbered. I had touched upon it in a very similar post I had written four years ago. You can also read this account on how players are numbered. And if you’re more curious about formations and their history, I recommend you read Jonathan Wilson’s Inverting the Pyramid.

To put it simply, number 1 is reserved for goalkeepers. Numbers 2 to 6 are for defenders, though some countries use either 4, 5 or 6 for midfielders. 7-11 are usually reserved for attacking midfielders and forwards, with 9 being the “centre forward” and 10 being the “second forward”.

Some of these numbers are so institutionalised that the number is sometimes enough to describe a player’s position and style. This has even led to jargon such as a “False Nine” (a midfielder playing furthest forward) or a “False Ten” (a striker playing in a withdrawn role).

There is less science to the allocation of shirt numbers 12 to 23, since these are not starting positions. One rule of thumb is to allocate these numbers for the backups for the corresponding positions. So 12 is the reserve goalie, 13 is the reserve right back and so on(with 23 for the squad’s third goalkeeper).

So how have teams chosen to number their squads in the FIFA World Cup that starts next week? This picture summarises the distribution of position by number: 

 

There is no surprise in Number 1, which all teams have allocated to their goalkeeper, and numbers 2 and 3 are mostly allocated to defenders as well (there are some exceptions there, with Iran’s Mehdi Torabi and Denmark’s Michael Krohn Dehli wearing Number 2 even though they are midfielders, and Iceland midfielder Samuel Friojonsson wearing 3).

That different countries use 4, 5 or 6 for midfielders is illustrated in the data, though two forwards (Australian legend Tim Cahill and Croatia’s Ivan Perisic) puzzlingly wear 4 (it’s less puzzling in Cahill’s case since he started as a central midfielder and slowly moved forward).

7 is the right winger’s number, and depending upon that position’s interpretation can either be a midfielder or a forward. 8 is primarily a midfielder, while 9 is (obviously) a striker’s number. Interestingly, five midfielders will wear the Number 9 shirt (the most prominent being Russia’s Alan Dzagoev). 10 and 11 are evenly split between midfielders and forwards, though two defenders (Serbia’s Aleksandr Kolarov and Tunisia’s Dylan Bronn) also wear 11.

Beyond 11, there isn’t that much of a science, but one thing that is clear is that Cox got it wrong – for it isn’t so “textbook” to give 12 to the reserve right back. As we can see from the data, 20 teams have used that number for their reserve goalies!

It’s like England has put their squad numbers into a little bit of a Mixer!

What’s in a shirt number?

There is a traditional way of allotting shirt numbers to football players. “Back to front, right to left”, goes the rule. The goalkeeper is thus number 1. Irrespective of the system used, the right back is number 2, and usually the left forward/winger is number 11.

Now, the way different teams allot numbers depends upon their historical formations, and how their current formations have evolved from those historical formations. The two historical formations that are the 2-3-5 (mostly played in Europe) and the W-M (which originated in South America).

You can read Jonathan Wilson’s excellent Inverting the Pyramid to find more about how formations evolved. This post, however, is about shirt numbers in the ongoing world cup.

Now, given the way numbering has evolved in different countries, each number (between 1 and 11) has a traditional set of roles involved. 1 is the goalie everywhere, 2 is right back everywhere. 3 is left back in Europe, but right centre back in South America. 4 is central midfielder in England, but centre back in Spain and South America. 6 is a central defender in England, left back in Brazil/Argentina and a midfielder in Spain.

These are essentially numbering conventions based on how numbering systems have evolved, but are seldom a rule. However, such conventions are so ingrained in the traditional football watcher’s mind that when a player wears a shirt number that is not normally associated with his position, it appears “wrong”.

For example, William Gallas, a centre back (and occasional right back for Chelsea) by trade moved to Arsenal in 2006 and promptly got the number 10 shirt, which is usually reserved for a central attacker/attacking midfielder (in fact, the number now defines the role – it is simply called the “number 10 role”). In the last season, West Ham used two successive left backs (Razvan Rat and Pablo Armero) last season, and both were allotted number 8 – traditionally allocated to a central midfielder.

In this post, we will look at the squads of the ongoing world cup and try and understand how many players are wearing “wrong” shirt numbers. In order to do this, we look at the most common roles associated with a particular number, and identify any players that don’t fit this convention.

Figures 1 and 2 have the summary of the distribution of roles according to shirt number.

shirt1

 

shirt2

As we can see, all number 1s are goalkeepers (perhaps there is a FIFA rule to this effect). Most number 2s and 3s are defenders, but there is the odd midfielder and forward also who wears this. Iranian forward Khosro Heydari wears 2, as do Greek midfielder Ioannais Maniatis and Bosnian  midfielder Avdija Vrsajevic.

The most unnatural number 3 (in his defence, he’s always worn 3) is Ghanaian striker Asamoah Gyan. Iranian midfielder Ehsan Aji Safi also wears a 3, contrary to convention.

As discussed earlier, midfielders from a few countries wear 4, but there are also two forwards who wear that number – Japanese Keisuke Honda and Australian Tim Cahill. This can be explained by the fact that both of them started off as midfielders, and then turned into forwards, but perhaps wanted to keep their original numbers.

5 is split entirely between defenders and midfielders, who also make up for most of the number 6s. The one exception to this is Russia’s Maksim Kanunnikov, who is a forward. Interestingly, as many as six number 7s (associated with a right winger in both 2-3-5 and W-M systems) are listed as defenders! This includes Colombia’s left back Armero who notoriously wore 8 for West Ham last year. This might possibly be explained by players who started off as wingers and then moved back, but kept their numbers. Two defenders – Costa Rica’s Heiner Mora and Australia’s Bailey Wright wear number 8.

Number 9 is again one of those numbers which is associated with a specific role – a centre forward. In fact, in recent times, there is a variation of this called the “false nine” (there is also a “false ten” now). We would thus expect that all number nines are number nines, but a few midfielders also get that number. Prominent among those is Newcastle’s Cheick Tiote, who wears 9 for Cote D’Ivoire.

10 is split between midfielders and forwards (as expected), but a few defenders wear 11. Croatian captain and right back Darijo Srna wears 11, as also does Greek defender Loukas Vyntra.

Beyond 11, there is no real convention in terms of shirt numbering. The only interesting thing is in the numbers allotted to the reserve goalkeepers (notice that no goalies take any number between 2 and 11). By far, 12 is the most popular number allotted to the reserve goalkeeper, but some teams use 13 as well. Then, 22 and 23 are also pretty popular numbers for goalkeepers.

Finally, we saw that Iran was the culprit in allocating numbers 2 and 3 to non-defenders. Greece, too, came up as a repeat offender in terms of allocating inappropriate numbers. Can we build a “number convention index” and see which countries deviated most from the numbering conventions?

Now, there are degrees in being unconventional, and these need to be accommodated into the analysis. For example, a midfielder wearing 4 (there are 6 of them) is pretty normal, but a forward wearing 3 is simply plain wrong. A forward wearing 8 is not “correct”, but not “wrong” either – this shows that we need more than a simple binary scoring system.

What we will do is to first identify the most common player type for each number, and every such player will get a score of 1. For every other player wearing that number, the score will be the number of such players wearing that number divided by the number of players wearing that number who occupy the most popular position for that number.

I’m assuming the last paragraph didn’t make sense so let me use an example. To use number 2, the most popular position for a number 2 is in defence, so every defender who wears 2 gets 1 point. There are two defenders who wear 2, compared to 29 defenders who wear 2. Thus, each defender who wears 2 gets 2/29 points. One forward wears 2, and he gets 1/29 point.

Taking number 10, the most common position for the number is forward (there are 17 of them), and they all get 1 point. The remaining 15 players who wear 10 are all midfielders, and they get 15/17 points (notice this is not so much less than 1).

This way, each member of each squad gets allotted points based on how “normal” his shirt number is given his position. Summing up the points across players of a team, we get a team score on how “natural” the shirt numbers are. The maximum score a team can get is 23 (each player wearing a number appropriate for his position).

Table 3 here has the team-wise information on correctness of shirt numbers. The team with the worst allocated shirt numbers happens to be Nigeria with 16.13. At the other end, the team that has allocated numbers most appropriately is Ecuador, with 21.

Country  Score
Nigeria         16.13
Costa Rica         16.85
Greece         17.22
Australia         17.45
Iran         17.69
Ivory Coast         17.74
Colombia         18.19
Cameroon         18.19
Argentina         18.29
USA         18.41
Italy         18.63
Portugal         18.66
Algeria         18.68
Honduras         18.69
France         19.02
Ghana         19.06
Croatia         19.08
Netherlands         19.20
Mexico         19.23
Brazil         19.28
Chile         19.37
Japan         19.52
South Korea         19.69
England         19.77
Russia         20.03
Switzerland         20.04
Uruguay         20.25
Spain         20.27
Bosnia & Herzegovina         20.37
Belgium         20.83
Germany         20.86
Ecuador         21.01

 

This, however, may not tell the complete story. As we saw earlier, conventions regarding numbers between 12 and 23 are not as strict, and thus these numbers can get allocated in a more random fashion compared to 1-11. There are absolutely no taboos related to numbers 12-23, and thus, misallocating them is less of a crime than misallocating 1-11.

Hence, we will look at the numbers 1 to 11, and see how teams have performed. Table 4 has this information:

Country  Score
Australia           7.45
USA           8.04
Iran           8.18
Greece           8.59
Nigeria           8.63
Ivory Coast           8.71
Costa Rica           8.84
Ghana           8.95
Croatia           8.96
Japan           9.06
Colombia           9.27
Brazil           9.29
Spain           9.66
Bosnia & Herzegovina           9.67
Uruguay           9.70
Honduras           9.71
Portugal           9.78
Italy           9.81
South Korea           9.83
Cameroon           9.83
Chile           9.87
Russia           9.94
England           9.97
Argentina         10.03
Switzerland         10.18
Netherlands         10.24
Algeria         10.30
Ecuador         10.34
Mexico         10.35
France         10.53
Belgium         10.88
Germany         11.00

 

Germany has a “perfect” first eleven, in terms of number allocation. Belgium comes close. At the other end of the scale, we have Australia, which seems to have the most misallocated 1-11 shirt numbers. Iran and Greece, which we anecdotally saw as having high misallocations are at three and four, with the United States at 2.

Note: The data is taken from the Guardian Data Blog. Now, this analysis should be taken with some salt since in the modern game, the division of players into “defender”, “midfielder” and “forward” is not straightforward. Where would you put a “classic number ten”? What about a wing back? And so forth.