After starting the season promisingly, Mannone is adamant Arsène Wenger's side can fight back and put this week's results behind them.
"We're really disappointed," the goalkeeper told arsenal.com. "It's not acceptable to play games like we did tonight and we need to focus on ourselves now and get back to the training ground and find a solution to come back. We need to come back stronger on Saturday.
"We need to win and I hope we get our heads in shape. We need to work as a team and we don't need to point the finger to anybody because it's a problem of a team.
"I think all over the field we didn't defend properly., didn't do well the job in midfield and didn't create many chances. At the minute, we need to get up from the floor and go again. The season has started well but now is the time to fight back.
"When you're going through these moments, you need to show character. Unfortunately we didn't today but I hope [in] the next game, it will be the Arsenal that the fans deserve. We're playing for a big club and we need to show it."