Neymar converted a first-half penalty kick and Barcelona held on at Anoeta Stadium for the first time since 2007, ending an eight-game winless streak.

"It's a victory that gives us confidence, especially because it came at a field where we had struggled so much," Barcelona coach Luis Enrique said.

Neymar calmly scored from the penalty spot after being brought down inside the area in the 21st minute, giving the two-time defending champion the advantage going into the return match at Camp Nou next week.

It was Neymar's second goal in two matches following an 11-game drought. He was rested in Barcelona's 5-0 rout of Las Palmas in the Spanish league on Saturday.

"We are happy because we hadn't won here in a long time," Barcelona midfielder Sergio Busquets said. "The result gives us an advantage, but they have a quality team and we've struggled against them over the years."

Barcelona lost five times and drew three in its previous eight visits to Anoeta. The last time Barcelona won in the northern city of San Sebastian was in the 2007 Spanish league with goals by Andres Iniesta and Samuel Eto'o.

The teams drew 1-1 in the league this season at Anoeta.

Iniesta was substituted at halftime on Thursday because of an apparent muscle injury.

Barcelona has reached the Copa semifinals for six straight seasons, winning three titles and finishing runner-up twice.

Real Sociedad won its lone Copa del Rey title in 1987.