Jeremy Mathieu scored the only goal of the game as the Azulones remained in ninth place, five points behind Real Betis in seventh.
“The team lacked belief in their football,” he told a Press conference. “They didn't have faith and you can't afford to do that against Valencia.
“We didn't have any intensity. It looked like we were winning, rather than trailing 1-0.
“We played better in the second half, but I still wasn't happy.”