Late goals from Ivan Ramis and Pedro Leon sealed a dramatic 2-1 win for Eibar and handed visitors Villarreal their first defeat of the new La Liga season.
Fran Escriba's side had looked set for a third straight domestic win when captain Bruno put them ahead from the penalty spot four minutes before half-time.
But the home side, looking to recover from five games without a win, responded in superb fashion only to be denied repeatedly by visiting goalkeeper Sergio Asenjo.
The home side started marginally better with Leon having the best early chance before a foul on Nicola Sansone in the box allowed Bruno to net the opener from the spot.
Asenjo's acrobatic stop from Florian Lejeune denied the hosts an equaliser before half-time, and after the break he also denied Leon, Sergi Enrich and Kike.
The home side finally got the leveller they deserved 10 minutes from time when defender Ramis swept home inside the box after Lejeune headed on a set-piece.
Cedric Bakambu came close to putting Villarreal back in front three minutes later when he headed agonisingly wide from a Rafael Santos Borre pass.
And Eibar grabbed their winner in the 87th minute following a swift counter-attack, with Enrich playing in Leon to hit a right-footed shot past Asenjo.
A first defeat of the campaign meant Villarreal missed the chance to move up to third in LaLiga, just two points behind leaders Real Madrid.