Complex sentence: The Athletic policy of recruiting only Basque-players has seen them frequently recruit from the canteras of other Basque clubs; indeed, the legendary Athletic player of the 1930s, Guillermo Gorostiza, was actually signed from Arenas Club de Getxo.
Split into simpler sentences: The Athletic policy of recruiting only Basque-players has seen them frequently recruit from the canteras of other Basque clubs. The legendary Athletic Bilbao player of the 1930s, Guillermo Gorostiza, was actually signed from Arenas Club de Getxo.