Athletic Bilbao dominated Granada in the Copa del Rey semi-final first leg but were only able to earn a 1-0 win on Wednesday thanks to a goal by Iker Muniain.
The Basques, who knocked out Barcelona in the quarter-finals, impressed at a raucous San Mames and had two goals disallowed for offside.
Inaki Williams had a low shot tipped round the post by Rui Silva and Raul Garcia was narrowly off target, before Muniain put Athletic ahead after 42 minutes.
Yeray Alvarez and Ander Capa`s strikes were ruled out as Athletic failed to build on their lead before the second leg in Andalusia on March 5.
"We feel good, to win at home and keep a clean sheet was very important, it`s a good result for the second leg. We`d have liked to expand the scoreline," Muniain said.
"Apart from that we had a good game, played intensely, at a good rhythm and we got a favourable result and we are happy."
Athletic spurned early chances before the electric Williams broke down the left flank and drove a low ball across for Muniain to convert from close range.
The hosts` domination continued after the break and Williams lashed over, while Yeray`s effort was ruled out because he and several other Athletic players were offside after a free kick.
Capa thought he had netted the second, only for it be disallowed after VAR referral, because Williams was offside and blocking the goalkeeper`s view.
Athletic have won the tournament 23 times, more than any side except Barcelona, and are favourites to reach their 38th final.
Real Sociedad host second-tier Mirandes on Thursday in the other semi-final first leg, with the return on March 4.
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