The Basque country is known for its historic claim to independence, but within its own borders there is an undervalued footballing rivalry.
Athletic Bilbao and Real Sociedad's histories are distinct but inextricably linked. Bilbao's Basque only policy is known the world over, but one of the principal reasons that makes it still a feasible one is the poaching of the very best young talent from rival clubs.
Indeed two of Athletic's star men this season, Spanish international Javi Martinez and European U-21 Championship winner Ander Herrera started their careers with Osasuna and Sociedad respectively. The San Sebastian side employed a similar policy until 1989 when fearing their ability to compete with Athletic and in the league generally they began singing foreign players, starting with John Aldridge (although there is a chance they thought they were buying Ian Rush).
That little brother complex has continued this season, Athletic's 2-0 win on Sunday completed a season double over their neighbours. Even more galling for Sociedad though is the circumstances in which the two victories have come about.
When they met In September, Sociedad had started the season brightly, winning two of their first four and drawing with Barcelona. Athletic meanwhile were struggling to adapt to the new physically and technically demanding ways of Marcelo Bielsa.
However, two goals from Fernando Llorente sealed their first league win of the season and sent Sociedad into a spiral that they didn't recover from until the end of November, Athletic meanwhile haven't looked back since.
On Sunday it was two special strikes from Ander Iturraspe that handed the hosts the spoils and kicked off a huge week for Athletic in perfect fashion. The win temporarily took them into the final Champions League slot - although Levante have since remarkably retaken their place in fourth - and this Thursday they play their biggest game on the European stage for many years as they travel to Old Trafford.
The tie is vitally important not just for Athletic's esteem but for La Liga's as a whole. With Real Madrid and Barcelona careering away at the top of the table, the question that has continually been asked over the past two years is are they just very good, or is the financial toll on the clubs outside the big two affecting the league's product as a whole?
The Europa League offers an insight to that question. With another two of Spain's strongest sides, Atletico Madrid and Valencia, still involved there is a chance to recreate the Portuguese feat of last season and have three semi-finalists or even an all Spanish final like that at Hampden in 2007.
The excitement surrounding Athletic's trip to Manchester was exemplified last week as well over 4,000 fans queued overnight for the only 4,000 tickets available to travelling fans. The unsurpressable feeling being that not only is it the opportunity of a lifetime but that they have a genuine chance of winning.
A strong side over the past couple of years, Athletic have jumped a level under the tutelage of Bielsa this term. The hard-running, hard-tackling style imposed by Joaquin Caparros has not been completely discarded, but softened by a crisp passing game that complements their more natural direct style and an intense pressing that allows them to win the ball back quicker and in more dangerous areas.
The Spanish squad that defeated Venezuela 5-0 last week contained four Athletic players, the same number as Real Madrid, and there were another four involved in the national squad preparing to take part in the summer's olympics.
However there is also a concern that a demanding schedule that has seen Bielsa's men play 17 games just since the turn of the year could already be wearing down a thin squad. Llorente, Ander and Iker Muniain were all replaced in the second-half against Sociedad to try and preserve some gas in the tank for the games against United, but with a cup final against Barcelona still to come, added to the weekly grind of fighting for Champions League football, there is a fear that Athletic's season could sizzle out in a very similar way to how Villarreal's did last season.
For now though, the belief remains that everything is possible and where better to keep a perfect season going than the Theatre of Dreams itself.
Around the league
Even before Jose Mourinho's very public indication last week that he plans to escape to the old country, Espanyol manager Mauricio Pochettino had been highlighted as a possible candidate for the Bernabeu hot seat. Unfortunately for the Argentine one stat might get in his way of an interview, his side's 5-0 defeat to Real now means in his seven games against the league leaders since taking charge in 2009 Espanyol's record reads: P 7 L 7 F 0 A 21.
Real Zaragoza's fans finally took a stand, or more accurately a walk. After a season dogged by ineptitude both on and off the field, they finally made their point to absent owner Agapito Iglesias by walking out with 13 minutes remaining of Sunday's encounter against Villarreal. The only downside was their side were trailing 1-0 when they left, by the end they had won 2-1 to claim only their fourth win of the season. Who'd be a fan eh?
The "who wants to be in Europe less than the Tories?" race took another intriguing twist this week as most of the contenders decided they did like the sound of this Champions League thing. Not only did Levante and Athletic win, but so did Malaga with three Golazos from Eliseu, Jeremy Toulalan and Santi Cazorla.
Meanwhile Atleti and Sevilla drew to ensure neither of them lost touch and the column's favourite local team Rayo Vallecano staged a brilliant second-half fight back to leave not only Racing Santander rocking but the three stands at Vallecas too. Rayo are now just four points off the Champions League themselves, if anything made a good Addidas ad these lads do!
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