In total, the 2,165 footballers fielded so far by big-5 league teams have played in 1,276 clubs from the start of their career at adult level to their 23rd birthday.

At the top of the table of teams having contributed most to the development of these players is Real Madrid Castilla.

Up until 23 years of age, 45 footballers under contract with big-5 league teams have played for the team currently coached by Zinédine Zidane.

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Among them, we notably find Juan Mata (Manchester United), Alvaro Negredo (Valencia) and Roberto Soldado (Villarreal).

For comparability reasons, the player development index only considers domestic league games.

A match played before the age of 21 is weighted double with respect to a game played between 21 and 23 years of age.

Moreover, the values are weighted according to the current employment rate of players in order to give more weight to teams having developed the most fielded footballers.

The team who contributed most to the development of Premier League players is Southampton, followed by Aston Villa and Dutch side Ajax Amsterdam. Chelsea and Everton also rank in the top five positions.

At the top of the tables in the remaining big-5 leagues are Empoli for Italian Serie A players, Bayer Leverkusen for German Bundesliga, Barcelona B for Spanish Liga and Olympique Lyonnais for French Ligue 1 footballers. Issue number 126 of the CIES Football Observatory Big-5 Weekly Post presents the data for the top 40 clubs per league.

The player development index could be particularly useful for leagues, national associations and international football governing bodies to set up systems of financial equalisation and/or reward mechanisms incentivising more teams to promote both the training and fielding of young talents.

Over the long term, this would have a positive effect on football as a whole.

For more information, please contact us at football.observatory@cies.ch