Barcelona's four-year dominance of the Copa del Rey is in jeopardy after a 2-0 defeat by Sevilla in the quarter-final first leg.
Pablo Sarabia blasted home Quincy Promes' cross to put the hosts ahead.
And Wissam Ben Yedder slid in at the back post following Ever Banega's deflected shot to double their lead.
Barcelona rested Lionel Messi and gave a debut to new loan signing Kevin-Prince Boateng, but he was replaced by Luis Suarez in the second half.
The Catalans have won the past four Spanish Cups, beating Sevilla in two of those finals - 2-0 in 2016 and 5-0 in 2018. The last time they failed to reach the final was 2012-13.
Real Madrid host Girona in their quarter-final first leg on Thursday (20:30 GMT).