Athletic showed promising signs early on, despite their torrid record against the Blaugrana, with Inaki Williams hitting a curling shot that troubled Marc-André ter Stegen before eventually being gathered.
Even so, Barca offered a reminder of their own threat, as rapid moves forward inside the opening quarter-hour resulted in João Félix’s effort striking the crossbar and Fermin Lopez forcing Unai Simón into an impressive save with his legs.
Ernesto Valverde had already lost Ander Herrera to injury during the warm-up and suffered another blow in the 26th minute, when Yuri Berchiche was forced to depart.
His side still stood toe-to-toe with Barca throughout the rest of the first half, and a toe was all that Inigo Lekue’s searching cross required as it bounced across the Blaugrana’s box, although it narrowly evaded both Oihan Sancet and Gorka Guruzeta.
Nico Williams also had an opportunity before the break, seeing his driven shot denied by Ter Stegen’s outstretched boot.
Joao Felix threatened to cause problems for Athletic after the restart, although Ferran Torres’ shot from his brilliant pass was blocked by Dani García before Simón made a superb double-save to deny the Portuguese forward and Fermin Lopez.
Joao Felix then drove through to create an opportunity for Lamine Yamal, who dragged his shot wide having been introduced from the bench just three minutes prior.
After doing well to cut inside Lekue, Joao Cancelo became the latest Barça player to be halted by Simón, whose strong hand pushed the ball behind.
Xavi Hernandez turned to Guiu in the 79th, and the debutant’s first touches outdid what even his wildest dreams could have imagined, with the 17-year-old taking Joao Felix’s pass in his stride and stroking home the goal that earned victory for Barcelona, taking them a point behind top spot in LaLiga.
Athletic, meanwhile, have suffered two defeats in their last three after previously going unbeaten since the opening day.
Flashscore Man of the Match: Joao Felix (Barcelona)
