A recent World Cup conversation got me thinking about how national teams at the 2026 World Cup differ in their club composition, that is, the club teams that supply the players on their roster.
My initial hunch was that teams drawing more from one or two clubs (e.g. Spain from Barcelona) might fare better due to pre-existing player familiarity. Of course, that logic depends on the quality of that club -- the team would only be as good as the team it drew from. To actually test it the quality of clubs would have to be normalized.
Nevetheless, out of curiosity I pulled the rosters for the 2026 World Cup as posted on Wikipedia and created some derivative charts and statistics:
- Club Concentration Metrics (Table)
- Club Concentration by National Team (Graph)
- Top Feeder Leagues (Graph)
- Club Count Distribution (Graph)
- Top Feeder Clubs by Player Count (Graph)
Takeaways
- Talent supply is heavily concentrated at the top. The big 5 leagues (the top leagues of England, Germany, Spain, France, and Italy) account for roughly 39% of all players. At the club level, Manchester City, Bayern Munich, PSG, Arsenal, and Barcelona lead the way above a long list of other feeder clubs.
- Most rosters are patchwork, where the median national team draws from 22 distinct club teams for the 26 players.
- High HHI nations like Saudia Arabia and Qatar have a closed-pool effect, where 90% of the players play in their own domestic league which causes the pool to draw from to be smaller.
- Domestic retention and concentration are correlated across all squads (r=0.83). Teams that keep more players at home do tend to be more club-concentrated because a domestic league is a far smaller pool of clubs to draw from. Spain is an outlier as its league has horizontal breadth -- six different La Liga clubs feed Spain's national team.
- The chemistry hypothesis is inconclusive, but is not "no effect." No trend across group stage → semifinals, but with N=4 in the two most advanced buckets and zero control for squad quality, this data can't distinguish "no effect" from "too noisy to tell."
Club Concentration Metrics
In this table:
- Top % = percentage of players from the top club
- Top-2 % = percentage of players from the top two clubs
- HHI = Herfindahl-Hirschman Index
- Effective clubs = 1/HHI
- Domestic % = percentage of players who play for a club team in their own nation
HHI refers to "Herfindahl-Hirschman Index" which is calculated by squaring the share of players for each club and then summing. Squaring makes dominant clubs push the index up faster.
A squad split 10/6/4/3/2/1 across six clubs gives:
(10/26)² + (6/26)² + (4/26)² + (3/26)² + (2/26)² + (1/26)² ≈ 0.209
| Country | Distinct Clubs | Top Club | Top % | Top-2 % | HHI | Effective Clubs | Domestic % |
|---|---|---|---|---|---|---|---|
| South Africa | 12 | Mamelodi Sundowns | 30.8% | 61.5% | 0.2041 | 4.9 | 73.1% |
| Czech Republic | 11 | Slavia Prague | 38.5% | 50.0% | 0.1982 | 5.04 | 65.4% |
| Saudi Arabia | 9 | Al-Hilal | 26.9% | 50.0% | 0.1746 | 5.73 | 96.2% |
| Qatar | 8 | Al-Duhail | 23.1% | 42.3% | 0.1568 | 6.38 | 96.2% |
| Spain | 13 | Barcelona | 30.8% | 42.3% | 0.1479 | 6.76 | 65.4% |
| Egypt | 14 | Al Ahly | 30.8% | 42.3% | 0.142 | 7.04 | 65.4% |
| Turkey | 16 | Fenerbahçe | 23.1% | 46.2% | 0.1272 | 7.86 | 57.7% |
| Germany | 13 | Bayern Munich | 23.1% | 38.5% | 0.1243 | 8.05 | 73.1% |
| Jordan | 14 | Al-Hussein | 26.9% | 38.5% | 0.1213 | 8.24 | 46.2% |
| Iran | 14 | Tractor | 15.4% | 30.8% | 0.0976 | 10.24 | 65.4% |
| New Zealand | 19 | Auckland FC | 23.1% | 34.6% | 0.0917 | 10.9 | 0.0% |
| Argentina | 19 | Atlético Madrid | 23.1% | 30.8% | 0.0888 | 11.27 | 7.7% |
| England | 16 | Manchester City | 15.4% | 30.8% | 0.0888 | 11.27 | 80.8% |
| France | 18 | Paris Saint-Germain | 19.2% | 26.9% | 0.0799 | 12.52 | 30.8% |
| Portugal | 17 | Paris Saint-Germain | 15.4% | 26.9% | 0.0799 | 12.52 | 19.2% |
| Uzbekistan | 16 | Pakhtakor | 11.5% | 23.1% | 0.0769 | 13.0 | 61.5% |
| Mexico | 21 | Guadalajara | 19.2% | 26.9% | 0.071 | 14.08 | 46.2% |
| Belgium | 18 | Club Brugge | 11.5% | 23.1% | 0.068 | 14.7 | 11.5% |
| Netherlands | 19 | Brighton & Hove Albion | 11.5% | 23.1% | 0.068 | 14.7 | 7.7% |
| Brazil | 20 | Flamengo | 15.4% | 23.1% | 0.0651 | 15.36 | 26.9% |
| Iraq | 20 | Al-Talaba | 11.5% | 23.1% | 0.0621 | 16.1 | 38.5% |
| Australia | 22 | Melbourne City | 11.5% | 19.2% | 0.0533 | 18.78 | 19.2% |
| Canada | 22 | Los Angeles FC | 11.5% | 19.2% | 0.0533 | 18.78 | 7.7% |
| Norway | 22 | Bodø/Glimt | 11.5% | 19.2% | 0.0533 | 18.78 | 15.4% |
| Paraguay | 22 | Palmeiras | 11.5% | 19.2% | 0.0533 | 18.78 | 11.5% |
| South Korea | 22 | Jeonbuk Hyundai Motors | 11.5% | 19.2% | 0.0533 | 18.78 | 26.9% |
| Uruguay | 22 | Flamengo | 11.5% | 19.2% | 0.0533 | 18.78 | 0.0% |
| Austria | 22 | RB Leipzig | 7.7% | 15.4% | 0.0503 | 19.88 | 11.5% |
| Curaçao | 22 | Miami FC | 7.7% | 15.4% | 0.0503 | 19.88 | 0.0% |
| Ecuador | 23 | Atlético Mineiro | 11.5% | 19.2% | 0.0503 | 19.88 | 7.7% |
| Ghana | 23 | Auxerre | 11.5% | 19.2% | 0.0503 | 19.88 | 3.8% |
| Scotland | 22 | Celtic | 7.7% | 15.4% | 0.0503 | 19.88 | 30.8% |
| Senegal | 22 | Nice | 7.7% | 15.4% | 0.0503 | 19.88 | 0.0% |
| Japan | 23 | Sint-Truiden | 7.7% | 15.4% | 0.0473 | 21.12 | 11.5% |
| Panama | 23 | Saprissa | 7.7% | 15.4% | 0.0473 | 21.12 | 7.7% |
| Algeria | 24 | Lille | 7.7% | 15.4% | 0.0444 | 22.53 | 11.5% |
| Bosnia and Herzegovina | 24 | Schalke 04 | 7.7% | 15.4% | 0.0444 | 22.53 | 3.8% |
| Colombia | 24 | Crystal Palace | 7.7% | 15.4% | 0.0444 | 22.53 | 3.8% |
| Croatia | 24 | Manchester City | 7.7% | 15.4% | 0.0444 | 22.53 | 7.7% |
| DR Congo | 24 | AEL | 7.7% | 15.4% | 0.0444 | 22.53 | 0.0% |
| Morocco | 24 | PSV Eindhoven | 7.7% | 15.4% | 0.0444 | 22.53 | 7.7% |
| Switzerland | 24 | Sevilla | 7.7% | 15.4% | 0.0444 | 22.53 | 7.7% |
| Tunisia | 24 | Club Africain | 7.7% | 15.4% | 0.0444 | 22.53 | 23.1% |
| United States | 24 | PSV Eindhoven | 7.7% | 15.4% | 0.0444 | 22.53 | 15.4% |
| Haiti | 25 | Colorado Springs Switchbacks FC | 7.7% | 11.5% | 0.0414 | 24.14 | 3.8% |
| Ivory Coast | 25 | Charleroi | 7.7% | 11.5% | 0.0414 | 24.14 | 0.0% |
| Cape Verde | 26 | Chaves | 3.8% | 7.7% | 0.0385 | 26.0 | 0.0% |
| Sweden | 26 | Derby County | 3.8% | 7.7% | 0.0385 | 26.0 | 11.5% |
Tournament Results Metrics
As of 7/12/26 ~ Semi-finals stage
| Stage | N | Mean HHI |
|---|---|---|
| Group Stage | 16 | 0.090 |
| Round of 32 | 16 | 0.062 |
| Round of 16 | 8 | 0.069 |
| Quarterfinal | 4 | 0.053 |
| Semifinalist | 4 | 0.101 |
Squad concentration shows no clean relationship with how far a team advanced — the four semifinalists were actually the most club-concentrated group on average, but with just four teams in that bucket and no control for underlying squad quality, that's not evidence of anything either way.
Club Concentration by National Team
Boxes represent distinct club teams and the darker ones contribute more players than lighter ones.