Ten-man Barcelona suffered their first home defeat of the season as they crashed 3-2 against Valencia on Saturday, leaving the door open for Madrid rivals Atletico and Real to move above them later in the weekend.
They remain top of La Liga on 54 points, but Atletico Madrid, who trail on goal difference, can go ahead of them with a draw against Real Sociedad, as can Real Madrid, a point behind, with victory over Athletic Bilbao.
It appeared service as normal as Alexis Sanchez put Barcelona ahead early on but strikes either side of halftime by Daniel Parejo and Pablo Piatti put Valencia in the driving seat.
Lionel Messi tied the score with a penalty on 54 minutes but the hosts were caught again on the counter through Francisco Alcacer.
Barcelona continued to struggle at the back and Jordi Alba was dismissed for a second yellow card with 12 minutes left.
The Catalan side now have just one win from their last four La Liga matches.
Before kickoff there was a minute's silence for former Spain coach Luis Aragones, who died earlier on Saturday.
Aragones trained Barcelona during the 1987-88 season and led them to victory in the King's Cup.
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