The BVB boss believes his side are back to their best following a 5-0 win over Freiburg at Signal Iduna Park on Saturday
The Bundesliga giants had won all of their league games prior to their trip to the San Paolo, where goals from Gonzalo Higuain and Lorenzo Insigne consigned them to defeat.
However, they showcased their best form in Saturday's 5-0 victory over Freiburg and Klopp believes his troops have turned a corner.
"We did not feel terribly under pressure," he is quoted as saying by the club's official website.
"We have analysed the game against Napoli in detail and drawn our conclusions. [Against Freiburg] we were in overdrive for the whole of the second half, which makes the job fun.
"So, we did not sit back after the 3-0 or the 2-0 and stepped on the gas. I thought the first half was good too.
"I was very satisfied with our pressing. Robert Lewandowski's [first] goal was outstanding."
BVB face Marseille in the Champions League on Tuesday and Klopp believes that home advantage could be crucial.
"Tuesday will be a challenge, but it will be a home game in front of a packed house."
Lewandowski and Marco Reus exchanged doubles for Dortmund against Freiburg, with Jakub Blaszczykowski adding the fifth.