Alejandro Berenguer slammed home a first-half penalty as Athletic Bilbao claimed a 1-0 first-leg lead over Atletico Madrid in the Copa del Rey semi-final.
Berenguer scored the winner from 12 yards in the 25th minute after Benat Prados was brought down inside the box.
Atletico banged on the door in the second half to avoid taking a defeat into the return leg and missed chances through Antoine Griezmann, Samuel Lino and Alvaro Morata.
The hosts thought they had a last-minute penalty but a VAR offside call denied them.
Bilbao were awarded a spot-kick after Reinildo Mandava clattered into Prados in the area and Berenguer dispatched into the bottom corner, sending Jan Oblak the wrong way.
Atletico struggled to make an impression for much of the first period and had a first sniff of an equaliser five minutes later when the ball fell for Lino outside the area but he curled over the crossbar.
There was a slight moment of panic in the 35th minute as goalkeeper Julen Agirrezabala attempted to keep the ball in play but had his pocket picked by Memphis Depay on the byline, but his shot on goal was heroically blocked by Aitor Paredes.
Atletico ended the half the more dangerous of the two sides and Griezmann was next to come close when his first-time effort flew just wide of the near post.
Bilbao had a glorious chance to double their advantage after the break as Unai Gomez’s effort was parried by Oblak into the path of Asier Villalibre but he could only divert the rebound into the side-netting.
Chances began to fall at either end and this time Lino decided to let rip from the left edge but he curled just wide of the post.
Atletico’s eagerness to not take a loss away to Bilbao became a lot more evident as they began to commit players up the pitch, with Griezmann next to come close when his effort from six yards was blocked behind by Agirrezabala again.
Atletico spurned another golden chance to equalise when Morata failed to divert a dangerous whipped cross on target.
Agirrezabala was beaten for the first time in the match when Angel Correa smashed past him inside the box but Bilbao defender Inigo Lekue was waiting behind the keeper to clear the ball off the line and keep the clean sheet intact.
Atletico thought they were given a last-gasp chance to equalise when referee Alejandro Hernandez pointed to the spot after Dani Vivian tripped Morata inside the box but the VAR adjudged the striker to be offside in the build-up.
Madrid had yet another chance in stoppage time but Morata could only glance a header from close range wide.