Substitute Vicente Iborra struck seven minutes from time to keep Sevilla on course for a third straight UEFA Europa League title after a 2-1 win at Athletic Bilbao.
The visitors fell behind to an Aritz Aduriz opener but a quick equaliser from Timothee Kolodziejczak then Iborra's late winner gave Unai Emery's men the advantage heading into their quarter-final second leg next week.
The two sides headed into the game locked together on 48 points in the Spanish Primera Division but with four Europa League wins already behind them it was Sevilla who possessed the pedigree.
Pouring rain played a big part in a quiet opening period and the visitors did not get off to the best of starts with defender Benoit Tremoulinas limping off with just 12 minutes on the clock.
But the game burst into life on the half-hour mark when Bilbao's Inaki Williams burst through the visiting defence only to be denied by a fine save from David Soria.
Two minutes later the roles were reversed as Martin Krohn-Dehli threaded a through-ball which sent Vitolo racing clear, but the Sevilla striker was denied by Bilbao keeper Iago Herrerin.
The home side came close again five minutes before the break when Aduriz headed against the post from a Benat free-kick, then De Marcos fired inches wide on the stroke of half-time.
Three minutes into the second half the home side finally grabbed the lead when Aduriz rose to direct a fine header past Soria from a deep Iker Muniain cross.
But Bilbao's lead lasted less than 10 minutes as Emery's men rallied well and Kolodziejczak pounced to stab home the equaliser in a crowded box after an uncharacteristic mistake by Muniain.
Despite another miscued effort from De Marcos for the home side it was the visitors who were clearly in the ascendency and no doubt happy to sit on their away goal in anticipation of the home second leg to come.
But it got even better for the visitors three minutes from time thanks to the alertness of Iborra, who had only been on the field for nine minutes since replacing Ever Banega.
The in-form front man kept his nerve in the box to knock home from a neat pass by Kevin Gameiro and ensure his side are strong favourites to move closer towards a second successful defence of their crown.