Ahead of the contest, Blaugrana boss Ernesto Valverde claimed his side were down to the "bare bones"; however, that did not stop the hosts asserting their dominance early on, with Alcacer making their pressure count inside eight minutes.
It was fairly remarkable that Messi and Alcacer's strikes were Barca's only goals of the opening 45 minutes given their complete control of the game.
The away side again nearly went close in the 68th minute, but Inaki Williams was denied by a brilliant tackle from Alba when it looked as though the winger was through on goal.
Just four days after an encounter with Chelsea that was more exacting than the 3-0 scoreline suggested, the intensity understandably dropped in the second half, but Valverde's men were able to keep Athletic at arm's length to ensure they head into the global break in buoyant mood.
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The central point of this letter is that the national unit of the party and state units function in an autonomous manner, he said. We in Punjab have not been taken into the loop. "Two to three resolutions were kept, which were discussed thoroughly".
Coutinho, the club's record signing, struck the woodwork for a second time as he tried to lob Kepa after latching onto a clever lofted pass from Paulinho, who then smacked a curling shot of his own against the upright. After being teed up just outside the box, Messi unleashed an unstoppable shot into the bottom-right corner.
Messi almost handed Barca the lead after four minutes but his curling free-kick was tipped away by Bilbao shot-stopper Kepa Arrizabalaga.
But, despite their overwhelming dominance, and some simply sensational football, Valverde led his side into the dressing room at the break with just a two-goal advantage.
The second half got off to a slow start, with Barca taking their foot off the pedal.
As the second half passed by, the hosts struggled to find their levels from the first, with Athletic seeing more of the ball in opposition territory; however, failing to test Marc-Andre ter Stegen.