David Villa and David Albelda chipped in with first half strikes before Carlos Marchena added a third to sink the hosts.
Iranian hitman Masoud Shojaei's goal for Osasuna served only as a consolation in a match that saw Walter Pandiani given his marching orders midway through the second period and Miguel Flano sent off right at the death for the beleaguered Rojillos.
Although Juan Aranda had given Osasuna a bright start, the visitors took the lead 12 minutes in as David Villa put a predatory foot to Marchena's long ball over the top.
It was a consummate counter-attack, but eight-minutes later it was a different type of goal that saw Valencia double their advantage. Pablo Hernandez dribbled down the wing and passed to David Silva, whose shot was blocked by Ricardo. However, there was David Albelda to lob the stricken 'keeper from fully 25 yards.
Discipline began to wane as Javad Nekounam and Aranda picked up quick yellow cards, and Cesar of Valencia joined them in the referee's bad books, ostensibly for timewasting.
Two minutes before the break Aranda rose above Fernando Navarro, who otherwise had a fine game, but his headed scraped the post.
After the interval Osasuna again started strongly but were hit by a sucker-punch as Marchena scored the goal of a lifetime with an amazing volley that went in off the crossbar.
Walter Pandiani was then sent off for what referee Velasco Carballo saw as an unfair aerial challenge, but four minutes later Masoud's free header gave Osasuna an unlikely goal.
The linesman was then hit by a missle thrown by an increasingly furious home crowd as the game entered its closing stages. Miguel Flano missed a great heading opportunity, Pablo almost netted with a cross-cum-shot, and the energy proceeded until the end.
Some of it, sadly, was misdirected, Flano seeing red for a ridiculous kick-out at Ever Banega as the game drew to a close.