Arsenal substitute Gabriel Martinelli scored 36 seconds after coming off the bench and then made a second as the Gunners started their Champions League campaign with a fine win in Bilbao.
The Brazil winger replaced Eberechi Eze in the 71st minute and made an instant and telling impact, running on to Leandro Trossard’s flick and beating Unai Simon.
Martinelli then scampered past a defender on the left to cut the ball back to fellow sub Trossard, and his deflected shot went in off the post to seal the win with three minutes left.
The game had been deadlocked for much of the game as the first meeting of the sides failed to catch fire.
But the Gunners, bolstered by their summer signings and stronger-looking squad, kicked on to take all three points.
Athletic Club, in the Champions League for the first time since 2014-15, named an XI who had all never played in the competition. And experience proved key in the end.
Arsenal’s new striker Viktor Gyokeres had a busy but frustrating night and was replaced by Trossard after 65 minutes with Mikel Arteta playing Mikel Merino through the middle.
And the new men from the bench soon had their say to give the Gunners, who reached the semi-finals last season, a priceless away win.