It will be described as "parking of the bus" by some, due to the resilient nature that Real Sociedad defended. Although they were very deep, they did offer a threat going forward until they went down to 10 men just before half-time.
Jose Pinto for Victor Valdes was the only change from the Barcelona side that lost to Valencia, as they were their usual 4-3-3 formation. This was a bit of a surprise as it was expected that Andres Iniesta would start, but the midfielder should be in line for a return at Sevilla on Sunday.
For Real Sociedad, they lined-up in a 5-3-2 with speedy wide men Carlos Vela and Antoine Griezmann operating as the two strikers.
Sometimes teams are said to have five at the back when it's actually three, but the full-backs didn't advance very far up the pitch in this case, so it was clearly a five. From the picture below you can see how Real Sociedad were positioned. The back line in this instance was fairly straight, with the full-backs tucked inside.
Pedro and Alexis Sanchez are offering width, and the Sociedad defence are happy to allow them space knowing they would more than likely need to cross the ball.
Here, Xavi is in possession with both Cesc Fabregas and Jordi Alba giving him an option by making a run.
The midfield triangle for Real Sociedad was Gaztanaga sitting deep alongside the more advanced Gorka Elustondo and David Zurutuza.
It was Gaztanaga's role to pick up Lionel Messi when he dropped off into midfield. Elustondo and Zurutuza were tasked with the space around Xavi and Fabregas.
The forwards, Vela and Griezmann, would move in front of Sergio Busquets to make his life difficult, as was illustrated when he became the first player to be booked.
Barcelona dominated possession, but there was very little space between the lines. La Real were extremely compact, and that made it difficult for passes to breach the defence. With Sociedad giving Barca space on the flanks, the Catalans took the option to make the crosses.
In this photo, you can see that Alba has delivered the ball into the area, but there are seven Sociedad players against three Barcelona ones in the box. Needless to say, it was comfortably dealt with by the away side.
The problem when allowing Barca the freedom of the wide areas was that Barca's full-backs advance up the pitch and there was no one tracking there runs. They could get a bit of speed up before they entered the Sociedad's full back area.
This meant that the outside centre-backs had to move over in order to stop them from being outnumbered.
Sociedad countering at speed
Confident of retaining the ball, Javier Mascherano and Gerard Pique kept a high-line and pushed up. Neither player is particularly slow, but the pace of Griezmann and Vela was something they found difficult to deal with.
From a corner, the Real Sociedad defence got attracted towards the ball and Busquets was left unmarked to finish.
When Inigo Martinez was dismissed for appearing to say something to the referee, the size of the task was multiplied. Along with the injury to Mikel Gonzalez, it was the second change the defence was forced to make.
Even with 11 players, the statistics were completely contrasting, but in terms of shots on target, there was little between them.
For the remaining few minutes of the half, Sociedad were just 4-3-2. Straight away, it was evident how much extra room there was for Barcelona to maneuver.
In the second half, they moved to a 4-4-1 with two banks of four. Griezmann moved out to the left and Vela led the line, positioning himself around Busquets. Occasionally the two would swap places, and the Sociedad team as a whole would break up the play with a number of fouls and were a little more aggressive.
A couple of times in the first period, Alexis drifted between Jose Angel at left-back and Inigo Martinez on the left side of the three centre-backs. Because of the amount of defenders and how deep they were, it had little effect. Now with only two centre-backs, his diagonal runs were more of a threat.
Which was how the second goal came about; Fabregas released a perfectly timed ball behind the back four, which Alexis ran onto.
It was the only occasion when they were in this position. Alexis' shot hit the post and the unbelievable clearance from Elustondo struck his goalkeeper, Enaut Zubikarai, ending up in the net.
After this, Real Sociedad were holding on, but for all of Barcelona's dominance, there were few clear-cut chances. The ball was moved side to side, but there were few penetrative passes.
Former Barcelona assistant manager Henk Ten Cate said live on Sky Sports after the match that it was the worst he had seen Barcelona in the last six years. That may have been a little harsh, but they did create very few chances. Both goals happened due to defensive errors.
Jagoba Arrasate got his tactics right and was just unfortunate that mistakes occurred at vital times.
Had Vela converted the chance before the opening goal or if Mascherano had been given his marching orders, it would have been a different tie.