In a stunning development in La Liga, FC Barcelona lost its match against Real Sociedad 3-1, which now puts Real Madrid as the sole leader with 63 points.
Earlier on Saturday, Real beat Elche in a convincing 3-0 win without their superstar Cristiano Ronaldo who was serving the last game of a three-match suspension.
Up until now, the top was shared by Barca, Real Madrid and Atletico Madrid in a three way tie, Barcelona with a slight advantage in goal differential.
FC Barcelona lost their second game in the last four matches despite being invigorated by their defeat of Manchester City in a Champions League tie on Tuesday.
However, after Alex Song turned Sergio Canales' pass into his own net, Lionel Messi tied almost instantly for FC Barcelona with a left-footed goal. But Real Sociedad scored two second-half goals from Antoine Griezmann and David Zurutuza handed Sociedad in the opening 15 minutes of the second half.
FC Barcelona failed to convert its possession into goals and midfielder Andres Iniesta admitted that Real Sociedad was the better team.