Athletic Bilbao B
Bilbao Athletic, officially named Athletic Club "B", is the reserve team of Athletic Bilbao, a football club based in Bilbao, in the autonomous community of Basque Country. The team will play in the Segunda División B in the 2018–19 season. Founded in 1964, the team holds home matches at the small stadium attached to the club's training facility at Lezama, or occasionally at San Mamés Stadium, with its 53,500-seat capacity, for important fixtures.
Basque derby
In the 1911 Copa del Rey, Real Sociedad withdrew in protest after their accusations that other teams, primarily Athletic Bilbao, were using ineligible foreign players, were rejected. Athletic went on to win the trophy without using the disputed players, although they did use some from Atlético Madrid which at that time was a branch of the older Bilbao club. This led to the Royal Spanish Football Federation introducing a rule for the next year's competition that all players must be Spanish citizens. Athletic chose to maintain the approach of using only local Basque players even when the regulations were relaxed some years later, a tradition which has continued into the 21st century. Real had a similar policy from the late 1960s, but it was dropped for foreign imports in 1989 when they signed the Republic of Ireland forward John Aldridge, and for non-Basque Spanish players in 2002 with the transfer of Boris from Real Oviedo.