Kylian Mbappé's replacement Endrick scored a first-half goal and Real Madrid won 1-0 at Real Sociedad in the first leg of the Copa del Rey semifinals on Wednesday.
Madrid was without Mbappé after he had tooth removed and was forced to miss practice Tuesday. The France star has scored six goals in his last five matches.
Endrick, an 18-year-old Brazil forward, scored in a breakaway after Jude Bellingham's long pass.
"Endrick has helped us a lot," Madrid coach Carlo Ancelotti said. "His goal was fantastic. He worked well up front and on defense as well. The team has been playing well."
On Tuesday in the first leg of the other semifinals, Barcelona and Atletico Madrid drew 4-4.
Both return matches will be played in April.
Ancelotti rested regular starters Thibaut Courtois and Federico Valverde. Courtois' replacement in goal, Andriy Lunin, played a key role in giving Madrid the first-leg advantage.
Madrid clinched its last Copa title in 2023. It was eliminated by Atletico in the round of 16 last season. Sociedad hadn't made it to the last four since it won its third Copa title in 2020, when it eliminated Madrid in the quarterfinals with a 4-3 win at the Santiago Bernabeu Stadium.
The Basque Country club had lost its last three matches against Madrid in the Spanish league.
Until now, the Copa's knockout rounds were played in single-elimination games. The final will be in Seville on April 26.