#1 SL Benfica
The three Portuguese giants Benfica, Porto and Sporting are all renowned for grooming top players, especially Portuguese or South American players. These clubs have an amazing scouting setup in the South American countries and have brought many players from the continent to the fore.
One can argue that all three clubs deserve to be on this list but Benfica probably deserve it the most. During the 2017 summer transfer window alone, the club sold Ederson Moraes to Manchester City, Victor Lindelof to Manchester United and Nelson Semedo to Barcelona.
These days, in addition to scouting some superb talents from South America, Benfica also have a strong scouting network in the former Yugoslavian countries, notably Serbia.
Some of the other major outgoing players from Benfica in the 2010s alone include Renato Sanches to Bayern Munich, Nicolas Gaitan to Atletico Madrid, Goncalo Guedes to PSG, Joao Cancelo to Valencia, Andre Gomes to Valencia, Ezequiel Garay to Zenit, Lazar Markovic to Liverpool, Jan Oblak to Atletico Madrid, Bernardo Silva to Monaco, Nolito to Celta Vigo, Nemanja Matic to Chelsea, Javi Garcia to Manchester City, Axel Witsel to Zenit, Fabio Coentrao to Real Madrid, Angel di Maria to Real Madrid, Ramires to Chelsea and David Luiz to Chelsea.