Arsenal striker Viktor Gyokeres continues in bandage after clash of heads with team-mate Gabriel

Gabriel Martinelli and Leandro Trossard came off the bench to score as Arsenal beat Spanish side Athletic Club to get their Champions League campaign off to a winning start.

Martinelli scored just 36 seconds after being introduced, with Belgium forward Trossard putting him through on goal in the 71st minute.

The Brazil winger then returned the favour, beating his man and giving the ball to Trossard to squeeze in the second in the 86th minute.

It was a tough match for Arsenal at times and Bilbao-based Athletic Club, back in the Champions League for the first time since the 2014-15 season, were backed by a vociferous home crowd and started the game extremely fast.

The home side had Arsenal pinned back for the opening period of the game, with Alejandro Berenguer causing particular problems for the Arsenal backline.

Arsenal struggled to get hold of the game in the first half but did have the best chance of the opening 45 minutes when Viktor Gyokeres put a diving header wide from close range.

Gyokeres ended the match with a bandage around his head after a heavy clash of heads with team-mate Gabriel, when the pair attempted to head the same ball goalwards.

The Gunners had been struggling to create a clear opening in the match before Mikel Arteta introduced Martinelli and Trossard in the second half.

Martinelli has had a difficult time in recent months, with a drop in form - and had started the last two games on the bench with new signing Eberechi Eze starting on the left wing - but will hope that the goal and assist will give him the lift he needs.

Arsenal have invested about £250m in their squad this summer and that depth was again on show as Arteta had quality options to choose from on the bench.

It was not one of the best performances from Arteta's side but, with three points and another clean sheet in the opening game, their Champions League campaign has started perfectly.

Athletic Club 0-2 Arsenal: Gabriel Martinelli and Leandro Trossard give Gunners winning Champions League start