Goalkeeper Manuel Almunia believes Arsenal's shock defeat to Hull City last weekend has given the players a much-needed wake-up call.
Gunners boss Arsene Wenger was furious after his side gave away the lead to lose 2-1 at home to the Tigers on Saturday evening.
Arsenal relinquished top spot in the table to Chelsea with their second league defeat of the season, but Almunia claims Tuesday's 4-0 Champions League thrashing of FC Porto proved the players had learned from their previous mistakes.
"I think Arsene was furious before the Porto game and we said to ourselves that we had to play the game as Arsenal know they can. We had to show we were a very great team," he told the club's official website.
"Maybe some players were tired but Hull did very well. They are a strong team and we were surprised by them.
"I think Hull deserved the three points because our attitude wasn't very good during the game.
"But now we have togetherness, we are strong now, this is an important victory and it will give us more confidence.
"I hope at Sunderland (on Saturday) that we can show the strengths we have inside once again."