Leaders Real Madrid suffered just their second La Liga loss of the season in a shock defeat against Valencia.
Former West Ham striker Simone Zaza opened the scoring for the hosts with a spectacular strike and Fabian Orellana doubled the lead before Cristiano Ronaldo pulled a goal back.
Ronaldo could have snatched a point late on, but failed to hit the target with his looping header.
Zinedine Zidane's side remain one point clear of Barcelona with a game in hand.
Italian Zaza, 25, failed to score in 11 appearances for the Hammers and broke down in tears at the weekend after his first goal since May. His fourth minute strike against Real at the Mestalla was brilliant, spinning in the area and shooting into the top corner.
Just five minutes later, Orellana finished off a flowing counter-attack, but just before the break Ronaldo's towering header - on his 700th club appearance in his career - from Marcelo's cross gave Los Blancos hope.
Welshman Gareth Bale came off the bench for just his second appearance after a three-month injury layoff for the final half hour and nearly scored, but his point-blank header was blocked by Enzo Perez.
Victory allows struggling Valencia to move up to 13th in the table, with boss Voro their third manager of the season.