 The transfer came into effect on 1 July 2009.He made his debut for the club in a 2–0 win over Sevilla FC.On 1 May 2014, Mathieu looked to have scored the goal to send Valencia through to the 2014 UEFA Europa League Final when he scored off of Ricardo Costa's lay-off, making the score 3−0 against Sevilla (3−2 on aggregate) but Stéphane Mbia scored a 94th-minute header to win the semi-final on away goals for the Andalusian side.