Mikel Oyarzabal slotted home a late penalty to fire Real Sociedad into the Copa del Rey final with a 1-0 win over Basque rivals Athletic Bilbao on Wednesday, securing a 2-0 aggregate semi-final triumph.
American coach Pellegrino Matarazzo has turned La Real's fortunes around since arriving in December and his side will face Atletico Madrid in the Seville final on April 18, after they ousted Barcelona.
Already holding a 1-0 lead from the first leg at Athletic's San Mames, Real Sociedad produced a sturdy display at the Reale Arena to knock out the 24-time winners.
"Very proud of what the boys have done, over the past two months, it's pretty amazing," said Matarazzo. "Our first match was on the fourth of January. And we just reached the cup final.
"The football we're playing is effective and we want to continue. We're in the final and we want to win it."
Real Sociedad have now not lost in their last 10 derby clashes at home against Athletic, whom they beat in the 2020 final, and rarely looked like letting their advantage slip.
"I think having the one goal advantage helped, we managed the tempo well," Real Sociedad defender Jon Martin told Movistar.
"We didn't want a lot to happen, and we did well."
La Real had the better of a tense first half, with Carlos Soler coming closest. The midfielder's free-kick, flying towards the top corner, was tipped over by Athletic goalkeeper Alex Padilla.
Matarazzo's team had more of the ball and forced the visitors back, albeit without carving out many more openings.
Athletic defender Aitor Paredes made a last-ditch block to keep former Valencia midfielder Soler at bay, and Goncalo Guedes drilled into the side-netting.
Ernesto Valverde's side improved in the second half and began to threaten La Real, again without finding a clear sight of goal.
Alejandro Berenguer fizzed a shot wide after Inaki Williams fed him on the edge of the box.
Los Leones were missing dangerous Spanish winger Nico Williams, who is sidelined indefinitely with a groin problem. (AFP)
Edited by Cecil Wong
