Per Mertesacker admits Arsenal were "lucky" on Wednesday but deserve to have qualified for the Champions League last 16.
Gunners defender Mertesacker believes complacency played a part in the 2-0 Champions League defeat at Napoli, and is just happy to be in the draw for the first knockout stage.
The Londoners all but secured their place in the last 16 with victory over Marseille last time out and seemed a little under par at the Stadio San Paolo, where goals from Gonzalo Higuain and Jose Maria Callejon earned Napoli all three points.
A poor night for Arsenal also saw midfielder Mikel Arteta pick up a red card midway through the second half.
With a crucial Premier League clash looming at Manchester City at lunchtime on Saturday, Mertesacker admits they must bounce back quickly.
"It's a strange atmosphere at the moment because we lost, by far, especially in the second half," the centre-back told Sky Sports.
"We were always on the back foot. We took a little break today, but we'll be back on Saturday."
The last-16 draw is made on Monday and Mertesacker added: "We gave 10 per cent less mentally because we were always thinking we were through.
"I think we were lucky today but we deserved (to go through) because we played a good group stage. Now we concentrate. We're second in the group for the draw next week."