Francesco Calzona, assistant to Napoli manager Maurizio Sarri, was impressed with the team's Europa League record after their 5-2 win over Legia Warsaw on Thursday.
Goals from Nathaniel Chalobah, Lorenzo Insigne, Jose Callejon and a brace from Dries Mertens saw the Partenopei top Group D with six wins out of six, 22 goals scored, and just three conceded.
"It was a pleasant surprise to win the group with six victories out of six," Calzona said. "We are satisfied, but the credit goes to the team who worked hard and made everything easier for us.
"We knew that we had an excellent strike force, but we didn't expect such a huge difference between goals scored and conceded.
"The team knows it has to take one game at a time and today we lacked a bit of intensity in defence. It's a shame about conceding two goals, but that's ok in the circumstances."
Calzona also spoke about Nathaniel Chalobah, the defensive-minded 20-year-old on loan from Chelsea, who opened the scoring against the Polish side.
"Nathaniel is a young lad who is learning the language and was a bit behind in terms of tactics when he arrived. He needs to improve his intensity in defence and be a bit more concentrated in forward movements too. He needs time to grow."