It acts as feeder club to Athletic Bilbao,[1] previously having the same agreement with Real Sociedad.

A number of famous players who appeared for Real Sociedad as well as other teams – and the Spanish national side – have graduated from the club, including Xabi Alonso, Mikel Arteta,[4] Javier de Pedro[5][6] and Yuri Berchiche.

[7] Sell-on fees from multi-million transfers involving Alonso and Arteta have provided funds for Antiguoko to improve their facilities.

Aritz Aduriz, Andoni Iraola[4] and Ander Murillo[8] were also youth products of Antiguoko, and later appeared professionally with Real Sociedad's Basque neighbours Athletic Bilbao, a club that had a formal agreement with Antiguoko for several seasons and continues to acquire its players on a regular basis.

The opponents in the league group include the academy teams of Athletic Bilbao, Real Sociedad and Osasuna, other clubs whose adult departments compete at various levels from La Liga down to Tercera División, and another strong youth-only organisation, Danok Bat.