 On 15 January 2015, he scored his first goal for "Barça" in a 4–0 Copa del Rey away win against Elche CF (9–0 on aggregate) after a spectacular direct free kick.Mathieu scored his first La Liga goal for the club against rivals Real Madrid in a 2–1 "El Clásico" win at Camp Nou on 22 March 2015.In the team's next fixture, Mathieu scored the only goal in a 1–0 win at Celta de Vigo, to keep his team four points clear at the top of the league.