Speaking to the club's official website, Mascherano said: "It hurts a lot to lose the three points at home. It's possible that we won't stay top but there are still 16 matches left and we have to change things so that what happened on Saturday won't happen again.
"We should have been two or three up after half an hour. The last 10 minutes of the first half and all of the second, things were different. We lost our shape and it really showed.
"We still have to play our two closest rivals. It's clear that the margin of error from now until the end of the season is practically zero. Now it's us who have to push on. We have to improve things but not send out negative messages. It's all in our hands, and we still have a chance in all three competitions."
Real Madrid can also overtake Barca when they travel to Athletic Bilbao on Sunday night.