Following the Partenopei's 2-1 win, the Spaniard expressed his satisfaction at watching his side beat last year's Champions League runners-up
The Partenopei went ahead through a Gonzalo Higuain header and eased into control following Roman Weidenfeller's sending off, with Lorenzo Insigne firing in a rocket of a free kick in the second half to double the lead.
Although Pierre-Emerick Aubameyang pulled a late goal back, the Naples side held on and Benitez left the Stadio San Paolo immensely pleased with his squad's European endeavours.
"I am satisfied, as we did everything we talked about before the game," the Spaniard, 53, told Sky Sport.
"We knew Borussia were very dangerous on the break, but we talked about intensity and everyone helping out in defence.
"Last time I said the team was at 72 per cent and I still think we can improve a lot. Tonight against the European runners-up I have to be satisfied and positive, as it’s a great result.
"These new players – like Gonzalo Higuain, Jose Maria Callejon and Dries Mertens – are of international quality. It was all about giving the group confidence and players like Marek Hamsik and Lorenzo Insigne are enjoying this style of football. I am sure in one or two months it will be even better."
Napoli's next game in Group F will be at Arsenal on October 1.