The 50-year-old coach is struggling to come to terms with the fact that his side threw away a 3-1 lead in their epic encounter with the Serie A leaders.
Goran Pandev looked to have settled the game in the host's favor when he fired home on 68 minutes to make it 3-1 to the Partenopei. However, Juve came storming back in the final 20 minutes and snatched a point thanks to goals from Marcelo Estigarribia and Simone Pepe, leaving Mazzarri downcast.
"Today I see the glass half empty," he is quoted as saying by Sky the morning after a breathless encounter. "In the first half, we put on a show. But in the second half we paid for our efforts [in doing so]."
Mazzarri intimated that the added burden of Champions League football this season had taken its toll against a Juve side who have no European commitments.
"For us it was the fourth straight game," the Napoli boss said. "The concentration had to remain high for another 20 minutes. We fell and it was seen. At 3-1 up, we were thinking that we had it won, even though we were in trouble from a physical point of view."
However, on the plus side, on-loan Inter forward Goran Pandev delivered two goals of real quality which left Mazzarri feeling vindicated for bringing the much-maligned Macedonian to the San Paolo.
"Pandev is a player of the highest level, we are not surprised," the coach said. "He just had to get himself in the right condition."
The draw saw Napoli climb to sixth in the Serie A standings but it remains nine points adrift of leader Juventus.