Barcelona fell ten points behind Real Madrid as they crashed to a shock 3-2 defeat away at Osasuna in a match where Pep Guardiola made four changes to the team which defeated Valencia 2-0 in the Copa del Rey on Wednesday.
A makeshift midfield of Thiago Alcantara, Javier Mascherano and Sergi Roberto proved to be a costly mistake by the Barcelona tactician who left the likes of Xavi, Andrés Iniesta and Cesc Fabregas on the bench, perhaps with a view to the Champions League encounter with Bayer Leverkusen this coming Tuesday.
Barcelona fans exited the ground accusing the referee of poor decision-making but in truth, they had few grounds for complaint as for large chunks of the match, they were outplayed by a spirited Osasuna side who shot out of the blocks from the first whistle and took the lead just four minutes into the match.
The ball was played into Raúl García on the edge of the box who flicked the ball past Carles Puyol and into the path of the Serbian striker Dejan Lekic who comfortably slotted the ball past Victor Valdes giving José Luis Mendilibar's side the dream start.
Andrés Fernández produced a fine fingertipped save to prevent Lionel Messi's curling effort on 10 minutes before Osasuna doubled their lead with Lekic doubling his tally for the evening after he latched onto a superb Alvaro Cejudo cross from the right. Barcelona looked shellshocked as they struggled to play their free-flowing football on what was a relatively frozen playing surface.
Messi nearly pulled one back for Barcelona after a sumptuous one-two with Alexis Sanchez but his shot was well foiled by Fernández and down the other end, Cejudo tested Valdes's goal again with a fierce drive across goal.
Guardiola desperately needed to change his side and he responded by bringing on Isaac Cuenca and Cristian Tello for Puyol and Pedro in the hope of a much-needed comeback. And his substitions paid dividends almost immediately when Alexis Sanchez finished emphatically from Isaac Cuenca's low cross.
Many would have expected the hosts to buckle under Barcelona pressure but they responded only four minutes later, capitalising upon a Valdes mistake to regain their two-goal margin. The Spanish international's clearance was intercepted and swept to the left where Nino whipped in a teasing low cross which was diverted past the stranded Valdes at the near post by Raúl García.
Barcelona lacked a natural centre-half when Gerard Pique, who had a torrid game, was shortly replaced by Fabregas who assisted a second goal for the Catalans. Cristian Tello, who moments earlier had been denied a glorious curling goal by an impressive Fernández save, received a pass on the right-hand side of the 18-yard box before shifting the ball back onto his left-foot and unleashing a venomous effort past the Osasuna shotstopper. It was the 20 year old's second La Liga goal for his boyhood club after his strike against Real Sociedad earlier this month.
Only the woodwork prevented Osasuna scoring a fourth goal when Patxi Puñal's sweetly-struck shot from the edge of the box hit Valdes's left-hand post as Barcelona's defence was once again exposed.
Barcelona thought they had equalised in the 82nd minute when Alexis Sanchez converted from Messi's lofted cross but the goal was ruled out for offside after the ball had taken the deftest of flick-ons by Sergi Roberto.
Barcelona were pouring forward in search of an equaliser, Cristian Tello's shot looped onto the top of Fernández's goal and in the 94th minute Messi produced a sublime through ball for Fabregas who headed tamely at the keeper. That golden chance signalled the end of an enthralling encounter and one that the Catalan giants will potentially look back on as costly and pivotal in their hopes to retain the La Liga title.
With ten points separating Barcelona and Jose Mourinho's Real Madrid after their 4-2 win over Levante, it would take a serious hiccup on Madrid's behalf if Barcelona were to claim their Spanish crown once again.