Behrami feels that his side did not play well but insists that Napoli must stay calm ahead of their next clash with Marseille in Group F.
"We all knew that when you give away two goals to Arsenal at their home ground, it makes things even harder and is likely to make the result as bad as it can be," Behrami told reporters. "We had a very poor first half and then in the second half we pulled ourselves together. We stuck together and gave ourselves something to focus on, even if the result was not good for us.
"It is normal that when you play away from home in the Champions League, you will come up against a really tough team, but we really didn't expect to play that badly.
"Next we have two decisive matches against Olympique de Marseille and they will crucial to us qualifying. We have had one good match and one bad match, so let's not get carried away. Let's stay calm and get back to playing in the league on Sunday."
The defeat was Napoli's first under new manager Rafael Benitez.