The loss leaves Barca six points behind leaders Real Madrid.
Pique said: "I'm convinced that the team will give everything they've got to be fighting for the title at the end of the season."
The centre defender called on the Camp Nou faithful to "trust us."
Adding that, "there are may games still yet to be played, a lot of points up for grabs. Madrid is doing things a bit better and we have to turn this situation around. We are Barça and we'll move forward."