The Barcelona coach, Frank Rijkaard, had urged his side to be more ruthless in-front of goal after scoring just once in their last two matches. "Every goal need not be a work of art" he said.
But Barça continue to overelaborate in the final third and, after failing to kill off Athletic Bilbao, they surrendered their first-half lead and dropped two valuable points in the title race.
In the 79th minute Fernando Llorente ghosted in ahead of Lilian Thuram as both chased an Aitor Ramos centre. Both he and the French defender went to ground and with Thuram appearing to get the crucial last touch the ball was steered past Victor Valdes in the visitors' goal.
Barcelona responded and Leo Messi's cross was just too high for Eidur Gudjohnsen but it was Athletic who looked most like taking all three points with a last ditch challenge from Thuram preventing Llorente getting a winner.
Messi was back in the starting line-up in the league for the first time since his two-month injury lay-off and he was the player who gave Athletic most of their early problems.
The Argentine striker went close on 17 minutes only to be thwarted by Daniel Aranzubia in the home side's goal. But Valdes was also a busy man, getting down to stop a Javi Martinez effort on the half-hour.
Athletic had a great chance to take the lead soon after, but Aritz Aduriz blasted over when through. Barcelona made Athletic pay immediately with a goal on 35 minutes from Bojan Krkic. The 17-year-old finishing after Deco's had pounced on a mistake.
As tempers flared right on half-time the Athletic midfielder Javi Martinez went into the book for a crude challenge on Andres Iniesta and the second period began with the same intensity but it was Barça who held the ascendancy.
Messi was again the major threat and twice he penetrated the left-hand side of Athletic's defence, first crossing for Thierry Henry to shoot wide and then setting up Deco who blasted over.
But then Barcelona began to allow the home side back in. Xavi gifted Athletic possession on the edge of his own box and Javi Martinez drilled his shot hard and low to the Valdes' right only for the keeper to some how save.
With 11 minutes left on the clock Barcelona let the lead and part of their title hopes slip away. And things got worse later in the evening when Real Madrid edged Valladolid 3-2 to open up a nine-point lead.
Goals: Bojan (34) 0-1; Llorente (78) 1-1.
Athletic Bilbao (4-4-1-1): Aranzubia; Koikili, Ocio, Ustaritz, Iraola; Susaeta (Garmendia, 46), Orbaiz, Javi Martinez (Llorente, 69), D Lopez; Yeste; Aduriz (Ramos, 46). Substitutes not used: Del Horno, R Fernandez, Gabilondo, Prieto.
Barcelona (4-3-3): Valdes, Zambrotta, Puyol, Thuram, Sylvinho, Iniesta, Xavi (Edmilson, 63) Deco, Bojan (Gudjohnsen, 77), Messi, Henry. Substitutes not used: Oleguer, Pinto, Giovani, Abidal, Milito.
Booked: Athletic Bilbao Orbaiz, Martinez, Susaeta.