Hugo Duro struck twice for Valencia as they earned a 3-0 victory over Atletico Madrid on Saturday in La Liga.
The hosts have started the season well after flirting with relegation until the final day of the previous campaign, and this was their best performance yet under coach Ruben Baraja.
Atletico coach Diego Simeone has faced many different Valencia coaches over almost 12 years in charge and had only lost twice before defeat at Mestalla in 28 games.
Defeat was the worst way for Atletico to prepare for the start of their Champions League campaign on Tuesday at Lazio.
"They came into the game with a lot more intensity and if you don't match it ... it's impossible to win any game," said Atletico goalkeeper Jan Oblak.
"They deserved to win, we have to congratulate them and we have to look in the mirror. We know we can give a lot more than we gave today.
"We lacked everything today ... we played a very bad game, we lost 3-0 and that hurts a lot."
Spanish striker Duro, 23, slid in at the near post to fire into the roof of Oblak's net after just five minutes.
The forward kept his composure to beat the Slovenian goalkeeper again when sent through on goal by Fran Perez after shrugging off Axel Witsel.
Javi Guerra struck the third goal with a fine solo move and finish inside Oblak's near post as Los Che continued to dominate.
Valencia could have increased their lead but Oblak saved well from Diego Lopez in the final stages, among other openings.
Earlier Athletic Bilbao earned a convincing 3-0 win over Cadiz to climb provisionally second behind leaders Real Madrid, who host Real Sociedad Sunday. Champions Barcelona welcome Real Betis later Saturday.
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