Milan blew a 2-0 lead to drop two points in Naples as Luca Cigarini and German Denis both struck in injury-times for the hosts.
Pippo Inzaghi and Pato had Milan two goals up inside the first six minutes and Leonardo said: “The result is disappointing and leaves us with a bitter taste in our mouths.
“The result is disappointing and leaves us with a bitter taste in our mouths,” said Leonardo.
“We had such a strong start and scored two goals in the first six minutes. In a way the goals were too early, as we knew that controlling the match for 85 minutes was going to be tricky.
“The finale was just incredible. [Ignazio] Abate's red card is the only reason I can think of as to why we ended up drawing this game with Napoli.
“With hindsight I could've avoided it by substituting him with Massimo Oddo, as I knew Abate was already on a yellow card.
“Nonetheless, the team is aware it played a great game and this result will not hit our confidence. The draw is a bit disappointing, but the performance remains positive.”