Sevilla's chances on a badly cut-up pitch at the Mestalla were dealt a blow shortly before the break when Mali striker Frederic Kanoute was shown a second yellow card for a dangerous tackle on Valencia captain Carlos Marchena.
Two minutes after the restart, Mata drove the ball high past Sevilla goalkeeper Andres Palop from the edge of the box and Hernandez made sure of victory with 10 minutes left when a first-time shot off his shin flew into the net.
Atletico Madrid's campaign got off to a poor start earlier on Sunday when they were thrashed 3-0 at Malaga. Villarreal squandered a 1-0 lead at Osasuna to draw 1-1, while promoted Xerez lost 2-0 at Real Mallorca and had two players sent off in their first match in Spain's top flight.
Athletic Bilbao beat visiting Espanyol 1-0 and Roberto Soldado netted three to propel Getafe to a 4-1 win at Racing Santander. Nabil Baha gave Malaga the lead against Atletico with an acrobatic volley in the 34th minute and Manu Torres was on hand to smash in a loose ball from close range for their second just after the hour.
Xavi Torres completed the scoring with a header in the 89th minute with Atletico goalkeeper Sergio Asenjo stranded. The scale and manner of the defeat puts unwelcome pressure on Atletico coach Abel Resino, who was sent to the stands midway through the first half for protesting the referee's decision to caution Argentina forward Sergio Aguero.
Magical Diego
New Juventus signing Diego stole the show in only his second Serie A start with two stunning goals in a 3-1 win at AS Roma on Sunday. A mistake by Roma defender Marco Cassetti allowed Diego to charge towards goal from the halfway line before outmuscling John Arne Riise in the box and scoring with the outside of his boot for the opening goal.
Roma's Daniele De Rossi equalised for the hosts 10 minutes later. Diego was not to be outdone, however, and he ran on to Vincenzo Iaquinta's clever flick in the second half and bamboozled the Roma defence before rifling home. Fellow Brazilian Felipe Melo, sealed Roma's second league defeat with a fierce strike in injury time.
