It is a strange phenomenon. Barcelona, despite dominating La Liga over the past few years and recording remarkable victories at the Santiago Bernabeu, Mestalla and almost everywhere else, have not been able to win a single match at Anoeta since 2007.
Barca's last victory away to Real Sociedad came on May 5th of that year. Back then, Frank Rijkaard was in charge and the Catalan club were fighting to win La Liga for the third season in a row, ultimately missing out to Real Madrid due to their inferior head-to-head record in the two meetings with Los Blancos.
Claudio Bravo was in goal for the Basque outfit that day as Andres Iniesta and Samuel Eto'o scored the goals for a Barca side also featuring Lionel Messi. Real Sociedad suffered relegation at the end of that season, but ever since their return to the top flight in 2010, they have been able to frustrate the Blaugrana at Anoeta.
La Real produced a 2-1 win towards the end of the 2010-11 season, came back from two goals down to draw 2-2 in September the following campaign, beat Tito Vilanova's team 3-2 in 2012-13, then defeated Tata Martino's men 3-1 in 2013-14 before successive 1-0 victories over Luis Enrique's side over the past two years. There was also a 1-1 draw at Anoeta in the Copa del Rey in 2014.
In 2010-11, Barca's trip to Anoeta came either side of the two Champions League semi-final meetings with Real Madrid and with a healthy eight-point lead over their fierce rivals in La Liga, Pep Guardiola picked a weaker team featuring Jose Pinto, Andreu Fontas, Martin Montoya, Jeffren and Ibrahim Afellay.
In the following season, the fixture followed an international break and Pep left a tired Messi on the bench along with David Villa. And although Cesc Fabregas scored twice to put Barca in control, Real Sociedad struck back with two goals themselves and the Argentine could not change his side's luck after coming off the bench. In both of those fixtures, the calendar played a part.
The following season saw Barca beaten 3-2 in one of only two Liga defeats that campaign under Tito Vilanova. Again, the Blaugrana had taken a two-goal lead (this time through Messi and Pedro), but the locals got back in it before half-time as Chory Castro scored and went on to win after Gerard Pique was sent off for a second bookable offence in the 56th minute. By that point, Barca were also comfortably clear in La Liga en route to 100 points and relaxation may have been a factor.
In 2013-14, Martino got his team selection all wrong as he picked Alex Song (who scored an own goal) in midfield, plus Adriano, Marc Bartra and Montoya at the back, while Xavi was left on the bench and did not feature for a single minute. The game came just four days after an impressive 2-0 win away to Manchester City in the Champions League, but there was no real reason to rotate here.
Meanwhile, Luis Enrique's first foray at Anoeta as Barca boss almost cost him his job. The Asturian coach left out Messi following a dispute on the training ground in the build-up to the match and the Argentine watched on as Real Sociedad took the lead after two minutes through a Jordi Alba own goal. The five-time Ballon d'Or winner came on at half-time, later joined by Neymar and Alves, but they were unable to reverse their team's fortunes.
Things turned around soon after that, however, and Barca went on to win the treble, followed by a Liga and Copa double last term. Still, though, they were unable to win at Anoeta in what was the second of three consecutive losses in the Primera Division.
Again, the timing of the fixture hardly helped as it came right in the middle of the two Champions League quarter-final clashes against Atletico. And to make matters worse, Luis Saurez was out through suspension, so Barca started with Munir El Haddadi, as well as Arda Turan and Rafinha in midfield. Mikel Oyarzabal scored the only goal of the game in the fifth minute.
Anoeta is not a particularly hostile stadium for visiting teams because the running track around the pitch means the local fans are farther away than at other grounds. However, Basques are fiercely proud and every game against one of the top teams is an opportunity to show their quality. In recent years, Real Sociedad have had plenty of that in attack, while Barca sometimes struggle versus physical teams like La Real.
However, there is no one reason for Barcelona's Anoeta curse, just as there was not when Real Madrid went just over 18 years without winning away to Deportivo La Coruna between 1991 and 2010. Sometimes, circumstances can get in the way and the problem can also become a mental one.
That is exactly what Luis Enrique will want to avoid and why he said on Saturday he has "no interest" in looking back in history because all of those games are gone now. On Sunday, Barca have an opportunity to end their Anoeta curse and with Madrid provisionally seven points clear in La Liga and the Clasico coming up next weekend, it would be a good time to put the hoodoo to bed.