The hosts raced into the lead within 90 seconds, although Michel's men were architects of their own downfall as Aleix García played a horrendous pass in front of his own area. Berenguer nipped in to pinch possession, before swivelling and finding the bottom corner with a low shot.
That was the third quickest goal the visitors had ever conceded in LaLiga, but they were undeterred, fashioning a pair of chances for Viktor Tsygankov, the best of which was saved.
Ernesto Valverde’s side were far from sitting back at the other end though, with Inaki Williams coming close to a second when he burst on to a ball down the right before cutting inside and hitting the post.
The striker would have two more opportunities as the break approached, the latter of them headed too close to the goalkeeper, although only after Girona’s Yangel Herrera had clattered agonisingly close from distance.
By the interval, Athletic had gone nearly eight hours without conceding, but their resistance was broken within four minutes of the restart when Tsygankov tucked home from inside the six-yard box, converting Ivan Martín’s bobbling cross.
It did not take long for the lead to be restored though, as Miguel Gutierrez cheaply lost possession to Gorka Guruzeta, who whipped a low ball into the area, where it was struck home by Berenguer.
Moments later, Inaki finally got his goal, benefitting from two Girona defenders leaving a long ball to each other, meaning the striker could control and strike into the far corner via the inside of the post.
A point-blank range save from Paulo Gazzaniga prevented Berenguer from taking home the match ball, as things threatened to get embarrassing for the visitors.
That stop proved crucial as Eric García nodded home Aleix García’s free-kick with quarter of an hour remaining, although their momentum was stalled by a five-minute stoppage for a medical emergency in the crowd.
They still created a hatful of chances in added time though, with Artem Dovbyk smashing into the side netting, while after Unai Simon had denied Sávio, Dani Vivian’s stunning goalline from Jhon Solís clearance ensured Athletic took the points.
Flashscore Man of the Match: Alex Berenguer (Athletic Bilbao)
