Barcelona lost 1-0 at Real Sociedad on Saturday while Real Madrid and Atletico Madrid both won to gain ground in the title race in La Liga.
Sociedad took the lead in just the fifth minute as 18-year-old Mikel Oyarzabal rose to head home Xabi Prieto’s cross.
Barcelona failed to find a response without the suspended Luis Suarez in the squad and remain without a win at the Estadio Anoeta since May of 2007, a span of seven games.
Lionel Messi had a few chances to score his landmark 500th goal for club and country but was denied by Geronimo Rulli, most notably from close range with five minutes to play. Messi has gone four games without a goal for Barcelona for the first time since April and May 2011.
With six games remaining, Barcelona’s lead atop the table shrunk to just three points over second-placed Atletico, while Real Madrid are four points off the lead in third.