Hamsik has described Napoli's performance as "terrible", but insisted that the Azzurri will learn from their first defeat of the campaign.
He told Sky Sport Italia: "We have to compliment Arsenal. They deserved the win. When you come up against a team like this one there are differences.
"You cannot start a game in the manner that we did. We gifted them with 15 minutes and two goals. They were just devastating early on and we were terrible.
"We can certainly learn and improve from this."
Benitez's men will look to bounce back in Serie A this weekend, when they take on newly-promoted Livorno.