Benitez said that he saw an improvement in his team from the 3-0 defeat to Atalanta BC, but admitted that Napoli must stop conceding so many goals.
"The match was spectacular and all supporters must have been glad to see the game," he told Rai Sport. "The positive side is we scored two goals, and the reaction of the team after the defeat in Bergamo, but it's not positive to go two goals down in the first half.
"We can win at the San Paolo. They were good, especially in the third goal with the one-two, and it was hard to stop them. The first goal was offside. It was clear, I don't have to say anything.
"We think we can win the second leg and if we do that then we can reach the final. A 1-0 win could be sufficient. It's a great shame we conceded the third goal, but our reaction was very, very positive."
Benitez took over Napoli last summer.