Borussia Dortmund centre-back Nevan Subotic feels his side can still make it out of Group F despite defeat to Arsenal.
An Aaron Ramsey header in the 62nd minute gave the Gunners the victory leaving Dortmund third in the group.
But the 24-year-old remains optimistic that last season's Champions League finalists can reach the knock-out stage.
He told reporters: "This was a really, really important game for us, there are only six group games and we've now lost two of them.
"It would have been good at least to have picked up a point. We can rectify things, however, providing we win our next home game against Napoli.
"Then we'll have every chance of qualifying, it's still very open in the group."
Subotic regrets his side's lack of concentration leading to the goal which decided the game.
"We were perhaps a little asleep," he added, "and had a reminder of exactly how good you have to be in the Champions League. Every mistake is punished.
"Everyone knows that with players like Bacary Sagna and Mesut Ozil, Arsenal are more than capable of whipping dangerous balls into the box, and that Giroud is very strong in the air.
"The deep cross comes in towards Olivier Giroud, he nods it down, and it's left to Ramsey to poke it in from a few yards out."
The home side were without their strongest centre-back Mats Hummels for the game which may explain the lapse at the back.
Dortmund face Napoli next in a must-win game for Jurgen Klopp's side.
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