Valencia left it late to grab the upper hand against Villarreal, scoring twice in stoppage time to secure a 3-1 victory away to their local rivals in the first leg of their Europa League quarterfinal on Thursday.
The result was harsh on the home side, who largely dominated possession yet were unable to create clear-cut chances against Valencia, who sit 12 places and 16 points above them in La Liga.
They were made to pay as a quick-fire double at the death from Daniel Wass and Goncalo Guedes, his second of the match, left them with a mountain to climb in next week's second leg.
"We knew it was going to be tough and we did what we had to do. We know they have their strengths but we defended them well, and played on the counter and we were able to get our goals that way," Guedes told Bein Sports.
"I don't think the result was undeserved. We had our chances, we were clinical and it is a deserved victory."
Guedes had opened the scoring after six minutes.
The Portugal forward was felled in the box by Santiago Caseres and although Valencia skipper Dani Parejo saw his penalty saved by Andres Fernandes -- the second consecutive game in which he has missed a spot-kick -- Guedes was on hand to net the rebound from close range.
After ceding the early advantage, Villarreal began to enjoy more of the ball, with Santi Cazorla causing problems for the Valencia backline.
Cazorla, who himself missed a penalty at the weekend, drew his side level from the spot on 36 minutes after Ezequiel Garay clumsily brought down Vicente Iborra and English referee Michael Oliver pointed to the spot.
Samuel Chukwueze was twice denied by Valencia goalkeeper Neto after the break as Javi Calleja's side looked to force a winner, but they gradually ran out of ideas and appeared happy to settle for the draw.
Yet with the clock having reached 90 minutes, Wass produced a sweeping left-footed finish against the run of play following Jose Gaya's storming run down the left-hand side to stun the home crowd.
Guedes then rounded off the scoring with the last kick of the game after Denis Cheryshev -- a former Villarreal player -- led an electric counter-attack as Marcelino's side put one foot in the last four.
"We weren't savvy at all," said Calleja in his post-match news conference. "There's another game to play (after going 2-1 down), but we played like there wasn't one.
"Now, everything is more difficult. It's a tough result to take but if you gift up chances and don't take yours then Valencia are always going to do what they did.
"We won't give up, of course. We'll go to Mestalla next week wanting to win and restore pride," he added.