Gabriel Martinelli’s instant impact gives Arsenal opening win at Athletic Bilbao

“Impactors,” Mikel Arteta called them, and Gabriel Martinelli made quite an impact at San Mamés. “Sometimes you just need a second to change the history of a football club,” the Arsenal manager said last spring, and although describing the goal that set up victory here in those terms would be pushing it, the beginning of a Champions League campaign in which they aspire to do just that underlined why he has insisted on the importance of strength in depth. On a night in which they were without seven key men and were yet to find a way through a club that are the ultimate in resistance the solution came from the bench.

One second it was not, but Martinelli had been on the pitch for only 36 of them when he was suddenly away, racing behind the Athletic Bilbao defence and slipping the ball under Unai Simón to put Arsenal into the lead with 18 minutes left. As if to prove the point, Leandro Trossard, another substitute who had come on just five minutes before him, had provided the pass for it and then added the second to secure the win. Last season they had paid for a lack of depth, Arteta had said; this season sees them start victorious thanks to the men waiting in reserve.

For much of a noisy night in which Noni Madueke had been the most consistent threat, Arsenal had struggled to carve out really clear chances. But then a loose ball dropped in midfield and Trossard got there first, sending it looping into space. Martinelli was on to it fast and if the first touch was a little heavy, the second was superb, seeing him escape Andoni Gorosabel and steer under the body of Simón.

High in a corner of San Mamés, Arsenal’s fans erupted. They had found a way through. And in the very last minute, they celebrated again when Trossard lifted a shot into the net. They had been part of a historic night for their hosts here, they had been in a contest too, but they had come through it, the first step towards what they hope is a historic season in Europe. One for which they have invested heavily, the cost of the starting XIs telling a story: €12m versus €567m.

Not that Athletic wanted that to be an excuse not to compete; it never has been, far from it. And while Arsenal dominated the ball in the opening minutes, it was with no particular intent, except perhaps to take some of the impetus from the game, to impose a control. Athletic soon stepped forward too, Mikel Jauregizar getting the first real shot off after five minutes, Gabriel Magalhães blocking the ball and Declan Rice catching the Athletic midfielder. That earned him a yellow which at times appeared to have him on a fine line.

Jauregizar then almost found Adama Boiro coming in at the far post and Alejandro Berenguer, dashing forward, was blocked by Gabriel. But here, on 20 minutes, Arsenal were starting to tilt the balance and Gorosabel had to make a superb interception inside the six-yard box ahead of Riccardo Calafiori and Eberechi Eze, who did not seem to see him coming. It had begun on the left, where Iñaki Williams had been caught by Jurriën Timber, who then combined with Madueke, and that was to become a well-worn path.

Yet while Madueke was repeatedly the threat, when Arsenal got their clearest sight of goal it came on the other side, when Mikel Merino set Viktor Gyökeres away. As he sprinted into the area on the left, though, Dani Vivian came to meet him and his shot lacked the power of direction to be more than a simple save for Simón. An even better opportunity followed when a long spell of possession that had started with a clever roll of his marker by Gyökeres, ended with the ball patiently worked into position for a cross from the right, the Swede diving in to head just past the post.

Gabriel Martinelli scores Arsenal’s first goal. He then provided the assist for Leandro Trossard for the second. Photograph: Albert Gea/Reuters

Gabriel then headed over, clashing with Gyökeres as he did so; his teammate was left bleeding, his head bandaged up. Arsenal were increasing the pressure, although Athletic did find a second wind and way out. Berenguer shot wide after he was slipped in by Williams and Robert Navarro was blocked by the seemingly insuperable obstacle of Gabriel. From the corner, Oihan ­Sancet headed over.

Madueke kept running. Sprinting clear, he cut into the area and while there was perhaps the chance to pull it back to Gyökeres, he had spotted a gap opened at the near post only to be denied by a strong right hand from Simón. A half-blocked shot skidded through to the keeper. And a dinked cross dropped into his arms: that was three approaches inside the opening eight minutes of the second half, but it was still not enough. At the other end, Williams worked the space for a shot that David Raya stopped by the near post.

The changes came, the test of that strength in depth upon which Arteta has placed such stress – and here it was, point proven almost immediately. Off went Gyökeres and Eze and on came the impactors.