Result is harsh on Armeros
Eibar were unable to respond to Aduriz's goal
Eibar failed to build on their fine start to the league campaign following last weekend's victory in Málaga as they slumped to a 1-0 reverse against Athletic Club in their first league outing of the season at Ipurua.
The Armeros controlled large spells of this encounter, but the Bilbao outfit took full advantage of their first chance of the afternoon to claim the winner.
The hosts made a bright start and penned the visitors in with their high, effective pressing game preventing Athletic from gaining a foothold in the middle third.
Cuco Ziganda's charges managed to even things up in the possession stakes halfway through the opening period, carving out their only opportunity of the game during this spell. With 38 minutes on the clock, Iñaki Williams shaped in a wicked cross from the right for Aritz Aduriz to nod the ball into the back of the net.
The Armeros totally dominated after the break, bossing proceedings and doing enough to have at least hauled themselves level.
On 70' Sergi Enrich came very close to levelling terms but the Eibar hitman's stabbed effort was kept out by Kepa Arrizabalaga, who two minutes later again came to the visitors' rescue when he gathered in Kike García's headed effort on the goalline.
Meanwhile, Athletic had the chance to have doubled their advantage on 77' but Marko Dmitrović was alert to deny Iker Muniain from point-blank range.
With seven minutes remaining, Enrich had one last opportunity but he failed to find the net when well-placed.
This result means that Eibar are ultimately unable to head into the first international break of the season with six points to their name. However, in their first two outings, the side has been convincing and shown that they're capable of going toe-to-toe with any opponents.