Martinelli and Trossard off the bench power Arsenal to 2-0 Champions League win at Athletic Bilbao

Arsenal opened their Champions League campaign with a 2-0 victory at Athletic Club as substitutes Gabriel Martinelli and Leandro Trossard combined to decide the game, prompting manager Mikel Arteta to hail the importance of his bench.

Martinelli struck 36 seconds after entering the match and later set up Trossard to wrap up the win, as Arsenal — missing several key players through injury — demonstrated the depth that has become central to the club’s plans this season. Arteta said he had taken the concept of "finishers" from rugby union and that players on the bench could be "at least equally important, or more important" than starters.

The breakthrough came on 72 minutes when Trossard flicked a ball into the area and Martinelli, who had been introduced for Eberechi Eze, advanced into the box and slotted past Unai Simón. Fifteen minutes later Martinelli provided the assist as Trossard, also a second-half substitute, finished to make it 2-0.

Arsenal began the match without injured regulars Martin Ødegaard, Bukayo Saka and Kai Havertz, with William Saliba only fit enough for a place on the bench. Arteta started five of his summer signings against the Basque side, underscoring the manager’s reliance on a broadened squad after a busy transfer window.

"The finishers are going to be more important this season sometimes than the starters," Arteta said. "We can change the game there, especially with the intensity that we play and teams start to drop off. I'm very pleased to see that."

Arteta acknowledged the emotional difficulty of leaving experienced players out of the matchday lineup but said he was encouraged by the substitutes' mentality. "Every time you give the line-up you are disappointing a lot of players. To have that spirit, I looked on the bench and I looked at him [Martinelli], and in his eyes I saw he was ready. Leo [Trossard] as well," he said.

Martinelli, 24, had struggled for form in recent months and had been dropped from the starting XI, with the arrival of Eberechi Eze and Noni Madueke adding competition on the wings. Arteta pointed to the Brazilian's attitude and commitment in praising his response after being named among the substitutes. Teammates rushed to celebrate with him after his goal, with Riccardo Calafiori pointing to the back of Martinelli's shirt in front of travelling supporters.

Victor Gyökeres, who started up front, showed encouraging signs of interplay and movement but again lacked a decisive end product. The striker, who has drawn attention for his running behind defences, clashed heads with Martinelli in the first half and continued to press despite bleeding from the collision; he later wore a bandage. Reporters at San Mamés noted his link-up play with Mikel Merino on Arsenal's left as a positive development.

Athletic Club created early pressure and posed a threat through Inaki Williams' pace and Oihan Sancet's influence in attacking midfield, but they were unable to convert several promising moments. Arsenal's win—secured in a stadium where they had to withstand sustained local pressure—serves as an early marker in a competition the club has yet to win.

Arteta said the substitutes' contribution "is going to be key this season," adding that the connection between players on and off the pitch was genuine and valuable. The result gives Arsenal three points in Group play and a morale-boosting start as they pursue their first Champions League title.