The Basques got their Liga campaign off to the perfect start by beating the capital club as they prepare for their Champions League qualifier in midweek
Real Sociedad got their 2013-14 campaign off to a winning start with a 2-0 triumph over Getafe ahead of their clash with Olympique Lyonnais on Tuesday.
Carlos Vela netted the first goal just before half-time with a delightful chip and then set up Haris Seferovic for the clincher with 20 minutes remaining.
The win continued Sociedad's good form from last season, when the Basque club finished fourth; their highest finish in La Liga in 10 years.
It was a good day for the Basque clubs in Spain as Athletic Bilbao also started with victory under new coach Ernesto Valverde, beating Real Valladolid 2-1.
Markel Susaeta gave his side the lead away from home just before the half-hour mark with a powerful drive, following a fine pass from Benat Etxebarria, but the hosts hit back just three minutes later when Patrick Ebert scored from Oscar Gonzalez's cut-back.
Athletic scored the decisive goal five minutes into the second half thanks to a half-volley from Iker Muniain after a sliced clearance from a Valladolid defender had come back off the post.
In the third match of the opening day of the La Liga season, Valencia defeated Malaga 1-0 thanks to a 64th-minute goal from captain Ricardo Costa.