Helped by a hugely controversial refereeing decision, Barcelona built a 2-0 advantage to take to Real Sociedad next week after the first leg of their Copa del Rey semifinal at the Camp Nou.

Both sides had chances in an incredibly open first half before the match and possibly the tie took a decisive swing in Barcelona’s favor. First, Javier Mascherano escaped a red card for tugging back the arm of Carlos Vela in the box as the Sociedad striker broke clean through on goal. Instead of it being the visitors that had the chance to go 1-0 up against 10 men, it was soon Barcelona who enjoyed that scenario. With Sociedad still reeling from the no-call, Sergio Busquets struck home a low shot following a corner. And with indignation coursing through their veins, Inigo Martinez was sent off, apparently for dissent.

The evening then took another bad turn for Jagoba Arraste’s side when they conceded a comical own goal on the hour mark as a wild clearance from Gorka Elustondo went into his own net off the head of his unknowing goalkeeper, Enaut Zubikarai.

Barcelona, despite displaying some skillful touches in the final third particularly in the opening half, will be disappointed not to have taken further advantage of their numerical advantage and all-but ensure their place in the Copa del Rey final. But it is defensively where Gerardo Martino may have greater concerns. For all the entertainment that was on show when the teams had 11 men apiece, Barcelona were worryingly open and exposed on several occasions. On another night the result could have been very different.

It was a first half full of chances and Real Sociedad twice came close to getting on the scoreboard in the opening minutes. Barcelona’s defensive frailties which were laid bare in a 3-2 defeat to Valencia at the weekend were once again on full show. Mascherano made an awful mess of trying to control a ball coming over the top facing his own goal to allow Vela to take control and knock it square to Antoine Griezmann on the edge of the box. Barcelona were left fortunate that the in-form Frenchman’s shot was straight at Jose Pinto. Griezmann was again less than clinical shortly after when, having again been found by Vela, he allowed the covering Jordi Alba to take the ball off his toes.

Barcelona’s forward pressure soon began to tell as they repeatedly came within inches of finding the back of the net. Cesc Fabregas failed to make clean contact on a deflected Dani Alves cross to allow Zubikarai to make a desperate save. An equally good chance was spurned by Alexis Sanchez moments later. The Chilean contrived to follow-up another saved effort from Fabregas by shooting into the wrong side of the side netting.

Lionel Messi was causing problems showcasing his tremendous ball control and vision dropping deep. But the Argentine’s finishing was not quite up to the rest of his game. Having seen his swept volley from Fabregas’ fine pass repelled by Zubikarai he fluffed the better chance on the rebound. He was more unlucky rather than wasteful when seeing his free-kick just fail to find the top corner and instead come back down off the crossbar.

What followed was a few seconds that would ultimately decide this first leg. Barcelona’s high line was exposed once more with Vela racing onto a long ball forward and holding off Mascherano as he closed in on goal. But as Vela went to strike a shot that was saved by Pinto, he was clearly having his arm dragged down by the tumbling Barcelona defender. It should have been a penalty and a red card. Sociedad got neither and their frustration was soon to boil over.

Barcelona went straight up the other end and won a corner, from which Pedro struck a deflected cross back into the danger zone and Busquets swiped it home inside the post. Sociedad were incensed, and Inigo Martinez clearly went too far in his outrage in the eyes of the referee and was sent on his way to the dressing room.

Things then went from the frustrating to the ridiculous for Sociedad. Supplied by a superb through ball from the excellent Fabregas, Sanchez’s finishing was again found wanting when directing his shot against the foot of the post. The Barcelona forward could then only look on in amazement as Elustondo, for reasons only known to him, elected to try and clear the ball back across his own goal and saw it clatter into the face of his own goalkeeper and bounce into the back of the net.

The floodgates might have subsequently been expected to open. Instead, Sociedad held their opponents largely at bay. Messi came closest to adding another but his flying volley was repelled by Zubikarai to keep the tie still alive heading to the Anoeta next week.

Barcelona 2-0 Real Sociedad (All Goals) 05... by ourmatch