"We have 12 points and it's a good number of points," Wenger told ITV Sport.
"I'm confident we can take another point or three in Naples if we play well. It will be difficult, like the other games away from home, but we have done well so far and we have to put that in our mind.
"We were well in control [against Marseille] and it was sometimes too easy. We lacked some sharpness overall, and we should have scored more goals."
Next up for the Gunners is Cardiff City on Saturday.