Valencia triumphed over their third-place visitors in an even battle, with Hugo Duro's header splitting the sides at their Mestalla stadium. Ernesto Valverde's Athletic were unbeaten in 14 matches across all competitions and had won their previous six.
However, they came up against another in-form side in Ruben Baraja's sturdy Valencia, who ground out their fourth consecutive La Liga victory to move seventh.
"The worst thing is we had control of the game, we got up there well but didn't make many dangerous chances," said Valverde.
Sergi Canos went off injured for the hosts early on, while Valencia goalkeeper Giorgi Mamardashvili made two saves from Nico Williams. The winger's brother Inaki Williams is away at the Africa Cup of Nations with Ghana and Athletic missed his dynamism in attack.
Oihan Sancet fired narrowly off-target for Athletic after the break, before Duro missed a huge chance from close range for Valencia. However, two minutes later he broke the deadlock by nodding Jose Gaya's looping cross beyond the reach of Unai Simon in the 61st minute.
Mamardashvili made a superb save to thwart Unai Gomez as the Basques chased the leveller, but Valencia held firm as Athletic suffered only their fourth top flight defeat.
After battling relegation last season and only securing survival on the final day, Valencia are enjoying a good campaign and their players celebrated joyfully with supporters at full time.
"It's a moment to enjoy, the fans, the atmosphere at the stadium, how the players have worked so hard... it's a fantastic day. I'm thinking I will enjoy these moments and let them stay in my retinas," said Baraja.
Barcelona, fourth, can now overtake Athletic if they avoid defeat at Real Betis on Sunday. League leaders Girona h
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