Sociedad took an immediate lead through an Ander Barrenetxea header in the very first move after kick-off without Atletico touching the ball.

The Mattress Makers responded in the 20th minute with Ademola Lookman equalizing with a well taken low shot from the just inside the penalty box.

The White and Blues managed to restore their lead at the stroke of half time after Atleti goalkeeper Juan Musso recklessly missed the ball he was attempting to punch out, connecting with Goncalo Guedes, with Mikel Oyarzabal converting the resultant penalty.

Both teams could not create chances in the second half until Julian Alvarez created some space in the 83rd minute before firing into the back of the net with Sociedad goalkeeper Unai Marrero rooted to the spot.

Diego Simeone's side did create great chances for the winner before full time but Alex Baena put his tap in over the crossbar while Johnny Cardoso pulled his shot wide after been put through on goal by Alvarez, forcing the match to extra-time.

The Txuri urdin had a golden chance to score in the first half of added time, but Musso managed to claw away a Ori Oskarsson follow up attempt before Argentine star Alvarez rattled the woodwork with a shot from outside the box as the match ended in a draw.

Alexander Sorloth and Alvarez saw their penalties saved by Marrero before Marko Marin converted the winning penalty for the Basque club to claim their fourth Cope del Rey title.

"It was important for us to control the game as best we could. Not to take risks," said Sociedad head coach Pellegrini Matarazzo to reporters after the triumph.

"We did a good job defensively. We had to suffer in the second half, but this is the character of the team. [Marrero] played a perfect game. I love the energy he has and that he overflows with the fans at certain moments. It was no coincidence that he stopped the two penalties."

Meanwhile his counterpart Simeone expressed disappointment on the outcome and rued the late missed chances during the first 90 minutes of the game.

"The outcome of the match could have been decided within the 90 minutes," said the Argentine head coach.

"Baena and Johnny [Cardoso] had chances to score, but they missed the target; those were good moments, but Real Sociedad's finishing was at the necessary level, and ours was not."

Atletico will turn their attention to the UEFA Champions League semi-final first leg clash against Arsenal at the Riyadh Air Metropolitano on April 29 while maintaining a strong finish in La Liga.

Real Sociedad upset Atletico Madrid to claim fourth Copa del Rey title