The Barca midfielder said: "Seven points is a big gap at this stage of the season, but we have to keep working.
"Once they scored, Real were able to dictate the game and play us on the counter attack. We were never comfortable."
However, Xavi added: "I believe we played better than Real Madrid. Particularly in the first-half, if Casillas hadn't saved that chance from Ronaldinho the result would have been different."