Cazorla found himself under a 60-yard punt forward at La Ceramica and with one touch, he cushioned the ball perfectly for Gerard Moreno to volley in.
Paco Alcacer had scored against his former club to put Villarreal ahead earlier in the first half.
Victory means Villarreal have taken 13 points out of 15 since La Liga returned earlier this month and now sit only three points behind stumbling Sevilla in fourth.
“We’re not going to put pressure on ourselves,” said Alcacer. “But we know what we can do and we want to finish as high as possible.”
While Villarreal have shot into contention for the top four, Valencia have plummeted away from it, this their third defeat in five games since the restart.
They have taken only four points in that time and with reports of unrest in the dressing room, coach Albert Celades appears unlikely to remain beyond the summer.
Valencia’s star striker Rodrigo Moreno stayed sat in the stands, staring into space, for several minutes after the final whistle.
“It’s a bad feeling,” said Celades. “We’ve played a game where we were by far the worse team. They were better than us.”
Yet for Villarreal, clinching fourth is now a very realistic possibility, even if a difficult final six games includes fixtures against Barcelona, Getafe and Real Sociedad.
It would be a remarkable achievement, not least for Cazorla himself, given the Spaniard’s incredible resurgence over the last two seasons following a spate of horrendous injuries.
The 35-year-old’s delightful touch for Moreno to volley in will go down as one of the goals of the season.
Goalkeeper Jasper Cillessen lumped the ball forward just before half-time and it dropped towards Cazorla outside the area.
He turned his body and cushioned it out of the air for Moreno to his right, who volleyed with his left and into the bottom corner.
Earlier, Alcacer had finished off Moreno’s lifted ball over the top and chose not to celebrate against the club that brought him through their youth system and gave him almost 100 appearances in the first team.
“Of course I wouldn’t celebrate, Valencia gave me everything,” Alcacer said.
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