Goals from Gonzalo Higuain and Lorenzo Insigne proved enough for the Serie A leaders to take the points in their opening Champions League clash against last season's finalists on Wednesday.
Benitez has revamped Napoli's squad in the close-season, bringing in Higuain in addition to the likes of Pepe Reina, Raul Abiol and Dries Mertens after losing Edinson Cavani to Paris Saint-Germain.
And the former Liverpool, Inter and Chelsea boss feels their triumph over Dortmund evidences the depth of quality present at the Stadio San Paolo.
"In such short rounds, the first match is extremely important and it's important to win it," Benitez said.
"We managed to achieve this result and defeated a very strong team.
"This result will surely boost the confidence of the players for the forthcoming match.
"We managed to change the players on the pitch and make a great performance, this means that the whole squad is strong and I trust every player."
