Osasuna were superb defensively and took advantage of some requisite luck and Barcelona's inability to finish their chances to hold the league leaders to a scoreless draw at El Sadar Stadium.
Osasuna's day got off to a rough start as Sisi was forced off after suffering an injury either to either left hamstring or knee. He went down initially after planting his weight on the leg as he tried to beat Carles Puyol to a ball and lasted only a minute as he tried to play through. He was replaced by Manuel Omwu.
Los Rojillos responded well, though, and despite all the usual possession and pressure you'd expect to see Barcelona put on their opponent, Osasuna stood tall and kept the game scoreless. Cesc Fábregas, playing in Lionel Messi's false nine role, was particularly ineffective wasting several great chances created by Neymar, who was excellent in the first half.
Barcelona defender Marc Bartra had a glorious chance to break the deadlock one minute from the break after getting a free header six-yards from goal off a corner. Instead of directing the ball into the empty net, Bartra header shot upwards and well over the crossbar.
The frustration continued early in the second half for Barca as Osuana's defense continued to stand strong and more opportunities were wasted. In the 54th minute Martin Montoya's cross on a counter attack just missed connecting with a sliding Neymar at the far post. There was nothing between the Brazilian and the goal but air, but he couldn't reach the ball in time.
In the end Barcelona simply couldn't unlock the excellent Osasuna defense as the Blaugrana dropped their first points of the season and opened the door for Atlético Madrid to move into first place.
Osasuna: Fernández, Bertrán, Loties, Arribas, Damia, De Las Cuevas, Lolo, Torres, Silva, Sisi (Omwu 5'), Riera (Puñal 68')
Barcelona: Valdés, Montoya, Bartra, Puyol, Adriano, Busquets, Xavi (Messi 68'), Iniesta, Fàbregas, Pedro (Tello 76'), Neymar