A youngster's dismissal on debut was the worst of it as Barca lost their second game in a row, and their second at home all season, prior to the Champions League final on Wednesday...
An under-strength Barcelona were greeted with the guard of honour from Osasuna at Camp Nou and began the brighter side, with young forward Pedro cutting in from the right early on and striking a shot just wide of the far post.
Bojan was the next to produce an effort on goal when he produced a sublime turn on the edge of the area before attempting a hopeful chip over the goalkeeper, only to miss the target.
The visitors tightened up thereafter and marked Samuel Eto'o tightly, limiting the Blaugrana to hopeful crosses and through-balls, even enjoying spurts of prolonged possession.
On 25 minutes, Osasuna took the lead from a corner, that had been conceded by Victor Sanchez after some shaky defending from Eric Abidal. Jaroslav Plasil delivered a swift corner, with Walter Pandiani running past Victor Sanchez at the near post to head home a bullet past Jose Manuel Pinto.
The goal lifted the visitors, who began looking a little more comfortable in possession, while Barcelona failed to create any telling chances.
It was Barca who would produce the next change, shortly before half time, when some persistence from Aliaksandr Hleb saw him eventually poke the ball to Samuel Eto'o, who squeezed a shot on target from a tight angle, forcing Ricardo into his first save of the game.
On the counterattack, Osasuna almost put the game beyond Barcelona when Juanfran cut in from the left and laid it off for Javad Nekounam, but the midfielder blazed his shot over the bar.
Osasuna came out after the break on the front foot, with Plasil robbing Pedro on the edge of Barcelona's area and finding Nekounam, who hit a decent shot on his left foot straight at Pedro.
However, it didn't take long for the hosts to find their stride, as Hleb began finding a little more room and they began fashioning half-chances: first a blocked Gudjohnsen shot from Pedro's cut-back and then an Eto'o shot that was sliced wide of the far post.
They edged even closer when a strong cross from Abidal was cleared only as far as Bojan, whose shot clipped the bar and went over.
The pace and rhythm from the hosts continued to rise up to and after the hour mark, using the width of the pitch in an attempt to stretch Osasuna, but still restricted to just a single shot from the edge of the area, from substitute Seydou Keita, that was straight at Ricardo.
Barca tested Ricardo again when Jeffren, Guardiola's third and final substitute, cut in from the right hand side and fed a provocative pass to Bojan, who showed great determination and composure to get on the end of it and slam a shot into Ricardo, who did well to stand up to the shot and keep it out, with just over a quarter of an hour of normal time left to play.
Catalan misery was compounded when substitute Marc Muniesa, in his first notable action of the game, made a sloppy last-ditch challenge on Hidalgo, but was harshly shown a straight red card.
The 17-year-old left the pitch near tears and the crowd - and Barcelona bench - reached fever pitch just moments before title celebrations were set to commence. A pitch invader managed to break onto the field of play and got right up close to the referee before being rushed by stewards and players then taken away.
In stoppage time, Osasuna forced Pinto into his first meaningful save when Nekounam blasted a strong, low free kick that the keeper managed to tip away from goal to keep his side in with a chance of at least equalising.
Moments later, Plasil did well to square for Pandiani right in front of goal, only for Hleb to chase back and make a crucial interception.
Sulmaan Ahmad, Goal.com
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