Victor Valdes admits Barcelona have taken "a backward step" after their 1-1 draw with Athletic Bilbao last night.
"Athletic Bilbao had one chance in the second-half and scored. They didn't create anything, but I admit they played well defensively.
"Today has been a sad day for us. We cannot give up, because there's still long way to go, but there's no doubt this cannot be repeated."
Barca teammate Andres Iniesta insisted: "We will never give up the Liga until it is mathematically impossible to win it. There are still many games left."