The match started frantically, as Frenkie de Jong fired wide with a close-range shot on the rebound before Pablo Ibanez had his effort blocked down the other end. Teenage starlet Lamine Yamal then weaved his way into the area and teed up a chance up for Ilkay Gundogan, who missed the target.
Cheered on by a partisan crowd in Pamplona, Osasuna caused their more illustrious opponents problems as Jose Manuel Arnaiz tested Marc-Andre ter Stegen with a shot which took a hefty deflection off Jules Kounde.
Ter Stegen was called into action again as the Barca defence was sliced open by Jesus Areso’s cut-back, but the resulting strike from Aimar Oroz was parried to safety by the German.
Ultimately, though, the visitors went into the break ahead thanks to Koundé, who brilliantly headed home from Gündogan’s cross in stoppage time.
Xavi reshuffled his pack with the withdrawals of Yamal and Sergi Roberto, as Ferran Torres and Joao Cancelo, who was making his debut following his loan move from Manchester City, entered the fray in their place.
Cancelo nearly made an immediate impact with a sublime cross towards Robert Lewandowski at the far post, but the Portugal international was in an offside position when doing so.
Los Rojillos were politely knocking on the Barcelona door without hammering it down, typified by some promising build-up play before Chimy Ávila’s strike, which sailed wide of the target. However, the hosts had their equaliser when the Argentine blasted in a fantastic long-range strike which clipped in off the post.
That joy was short-lived, though, as, in the 85th minute, Alejandro Catena was penalised and subsequently sent off for pulling down Robert Lewandowski inside the box. He proceeded to dust himself down and convert the resulting spot-kick to restore the champions’ lead.
As the match approached its climax, Osasuna manager Jagoba Arrasate was incandescent on the touchline when Iñigo Martínez appeared to bring down Ante Budimir right on the edge of the box and, instead of blowing his whistle, referee Miguel Ortiz waved play on.
Ultimately, though, Xavi’s men got the job done, and they now move up to third with 10 points from four games. Meanwhile, this defeat for Osasuna means they have now lost their opening two matches at El Sadar for the first time since the 2013/14 season, when the Pamplona outfit were relegated.
Flashscore Man of the Match: Jules Kounde (Barcelona)