Mikel Arteta believes Arsenal will not win the Champions League if they do not learn from their mistakes.
The Gunners suffered a defeat against Borussia Dortmund in their opening group stage fixture at Signal Iduna Park.
Ciro Immobile and Pierre-Emerick Aubameyang's goals saw the Bundesliga outfit seal a comfortable 2-0 victory.
The north London club's manager Arsene Wenger admitted that Arsenal's performance against Dortmund was disappointing.
The Gunners' skipper has urged his teammate to improve in order to avoid similar results in this season's Champions League.
"If you make the mistakes that we did, against top sides, we know that there is no chance to win the Champions League," Arteta explained.
"We encouraged them to do that by giving the ball away so many times in very difficult positions. They exploit the spaces very well and they put us under pressure."
"I am bitterly disappointed. I am very disappointed because we knew their strengths, what we had to avoid and what we did was encourage them to play their game."
"We have to react. We have to analyse what we have done wrong and try to improve. In four days, we have another game. That is the best thing, another game to try to react and improve," the Arsenal midfielder added.
Galatasaray and Anderlecht are the other two teams from Group D and their group-stage opener ended in a 1-1 draw at Turk Telekom Arena. The Emirates outfit will face the Turkish club in the next Champions League tie.
Arteta wants Arsenal to be lethal during the home fixtures in order to progress to the next stage of the Europe's Elite club competition.
"It has to be and we have to start taking the points [at home. Anderlecht and Galatasaray got a draw but we need to recover from this," the Gunners skipper told the club's official website.
"[We needed to improve on] our accuracy when we were taking the ball. When we were trying to play we kept giving the ball away straight away."