Teenage striker Endrick scored the only goal as a second-string Real Madrid side did enough to grab a nervy 1-0 win at Real Sociedad in the first leg of their Copa del Rey semifinal on Wednesday.

Real Madrid started brightly despite manager Carlo Ancelotti resting several key players and it took them 19 minutes to break the deadlock, with 18-year-old Brazilian Endrick providing a tidy finish from a counter-attack.

Vinicius made a great effort in defense to recover possession and quickly played the ball to Jude Bellingham who curled a brilliant long pass that Endrick took in his stride before firing a left-footed strike past the goalkeeper.

Alex Remiro made a stunning one-handed save of a close-range shot by Vinicius in the 25th minute while Sociedad's captain Mikel Oyarzabal wasted a golden opportunity for the equalizer a little later, firing a feeble shot from inside the box that Andriy Lunin easily held.

Right before the break, referee Jose Maria Sanchez stopped the game briefly after Vinicius, who was making his debut as Real Madrid captain, drew the referee's attention to fans allegedly targeting his team mate Raul Asencio with insults.

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Sanchez went over to the sideline to make both managers and members of the police aware of the situation, asking the stadium announcer to read a protocol statement against racist, xenophobic and violent speech.

The stadium announcer's words were greeted by whistles from a section of supporters, who also started targeting Vinicius Jr with abuse.

Real came out strongly after the break and dominated proceedings but were repeatedly denied by a Real Sociedad side who also created chances, with both keepers producing inspiring performances to frustrate their rivals' efforts.

The best chance came from Endrick, who almost extended Real's lead when he unleashed a bullet strike from the edge of the box that hit the crossbar, with Remiro making another fine save later to deny an effort by Bellingham.

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Real Madrid will have home advantage for the second leg on April 1, with Atletico Madrid hosting Barcelona a day later in the other semifinal after a 4-4 draw in their first leg on Tuesday.